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- Carl Sagan
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Astronomy Basics & Fun Facts
The stars never move in relation to each other. They are always the same distance apart (degrees across the sky) and in the same patterns.
The sun, moon, planets (and their moons), comets and asteroids do move (changes their positions among the stars).
Each star always rises and sets in the same positions on the horizons (from the same viewing spots).
All stars rise in the east and set in the west.
Some stars are visible every night of the year, all night long. This is due to their proximity to Polaris, the North Star. These are called Circumpolar Stars.(Example, the Little Dipper.) Circumpolar stars rotate counterclockwise around the North Star.
Polaris is the only star that is always in the same spot.
All stars rise (and set) approximately four minutes earlier each day. In a month the stars rise and set two hours earlier. Over the course of a year this amounts to 24 hours.
All stars are in the same positions at the same date and time each year. (Example: On November 15, 1997 at 10:30 p.m. the Little Dipper will be in the same position as on November 15, 1998 at 10:30 p.m.)
Each hour the stars move 15 degrees across the sky. During each 24 hours the stars all make one revolution around the earth (as the earth spins on its axis).
If you stay up all night, you can see just about all of the stars that can be seen from your latitude. The only ones you would not see are those close in the sky where to the sun is.
The stars are there during the daytime but we cannot see them because of the light of the sun.
The stars you can see change with your latitude. (Longitude is irrelevant.) People at the same latitude see the same stars, no matter in what country they are.
People in Los Angeles see the same stars as people in Tokyo and Beirut.
Polaris is almost directly above the earth's North Pole. The height Polaris is above your horizon (in degrees) is equal to your latitude. In Los Angeles, Polaris is about 34 degrees above the horizon.
At the North Pole, Polaris is 90¡ above the horizon (straight overhead). At the equator it is 0degrees above the horizon.
At the North Pole, all visible stars are circumpolar, none of them rise or set but they all travel in lines parallel to the horizon.
There are 88 official constellations. We can see about 60 of them from our latitude (over the course of a year, or a full night of stargazing).
The sun is a star. Unless you are properly equipped with filters and trained in their use, do not look at the sun with a telescope or binoculars.
Shooting stars are not stars. They are small grains of dirt entering the earth's atmosphere at high speed and burning up due to friction.
The Celestial Sphere is a convenient method for mapping the sky. It assumes that the Earth is at the center of a giant sphere on which are found all of the stars, planets, moons, comets, asteroids, galaxies, etc.
All these objects except the planets, moons, comets and asteroids of our solar system are at fixed points on this sphere (whatever the position of the Earth.) The Celestial Equator is an extension into space of the Earth's Equator.
The Celestial Poles are extensions of the Earth's poles. Each point on the celestial sphere has two coordinates, Right Ascension and Declination, which are similar to longitude and latitude on Earth. The R.A. and Dec. of the stars and deep space objects never change.
Those of the planets, moons, comets and asteroids of our solar system do change as they move among the stars.
As the Earth rotates on its axis, the Sun appears to travel from east to west around the Earth. On each day, the Sun is ina particular constellation, which means that if you could see the stars during daylight, the Sun would appear to be part of a constellation.
As the year progresses and the Earth revolves around the Sun, the Sun appears to be in different constellations. The path the Sun appears to travel through the constellations is called the Ecliptic and the constellations it passes through are known as the constellations of the Ecliptic or the Zodiac.
Traditionally, there were thought to be 12 constellations of the Zodiac but, in reality, the Sun passes through 13 constellations.
These constellations are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Ophiuchus, Sagittarius, Capricornus, Aquarius and Pisces.
The Sun is always in one of these constellations and moves completely through them slowly over the course of a year.
The Moon rises an average of about 50 minutes later each day. The full Moon rises at about sunset and sets at about sunrise. The new Moon rises and sets approximately with the sun, which is why we cannot see it.
The first quarter Moon, is straight overhead at sunset and sets at midnight. The third quarter Moon rises at about midnight and is straight overhead at sunrise.
A waxing Moon is in the shape of a D, that is, it bulges to the right. A waning Moon is shaped like a C, it bulges to the left.
© 1998 by Ben Balmages
INTRODUCTION
From our small world we have gazed upon the cosmic ocean for untold thousands of years. Ancient astronomers observed points of light that appeared to move among the stars. They called these objects planets, meaning wanderers, and named them after Roman deities -- Jupiter, king of the gods; Mars, the god of war; Mercury, messenger of the gods; Venus, the god of love and beauty, and Saturn, father of Jupiter and god of agriculture. The stargazers also observed comets with sparkling tails, and meteors or shooting stars apparently falling from the sky.
Science flourished during the European Renaissance. Fundamental physical laws governing planetary motion were discovered, and the orbits of the planets around the Sun were calculated. In the 17th century, astronomers pointed a new device called the telescope at the heavens and made startling discoveries.
But the years since 1959 have amounted to a golden age of solar system exploration. Advancements in rocketry after World War II enabled our machines to break the grip of Earth's gravity and travel to the Moon and to other planets.
The United States has sent automated spacecraft, then human-crewed expeditions, to explore the Moon. Our automated machines have orbited and landed on Venus and Mars; explored the Sun's environment; observed comets, and made close-range surveys while flying past Mercury, Venus, Jupiter, Saturn, Uranus and Neptune.
These travelers brought a quantum leap in our knowledge and understanding of the solar system. Through the electronic sight and other "senses" of our automated spacecraft, color and complexion have been given to worlds that for centuries appeared to Earth-bound eyes as fuzzy disks or indistinct points of light. And dozens of previously unknown objects have been discovered.
Future historians will likely view these pioneering flights through the solar system as some of the most remarkable achievements of the 20th century.
AUTOMATED SPACECRAFT
The National Aeronautics and Space Administration's (NASA's) automated spacecraft for solar system exploration come in many shapes and sizes. While they are designed to fulfill separate and specific mission objectives, the craft share much in common.
Each spacecraft consists of various scientific instruments selected for a particular mission, supported by basic subsystems for electrical power, trajectory and orientation control, as well as for processing data and communicating with Earth.
Electrical power is required to operate the spacecraft instruments and systems. NASA uses both solar energy from arrays of photovoltaic cells and small nuclear generators to power its solar system missions. Rechargeable batteries are employed for backup and supplemental power.
Imagine that a spacecraft has successfully journeyed millions of miles through space to fly but one time near a planet, only to have its cameras and other sensing instruments pointed the wrong way as it speeds past the target! To help prevent such a mishap, a subsystem of small thrusters is used to control spacecraft.
The thrusters are linked with devices that maintain a constant gaze at selected stars. Just as Earth's early seafarers used the stars to navigate the oceans, spacecraft use stars to maintain their bearings in space. With the subsystem locked onto fixed points of reference, flight controllers can keep a spacecraft's scientific instruments pointed at the target body and the craft's communications antennas pointed toward Earth. The thrusters can also be used to fine-tune the flight path and speed of the spacecraft to ensure that a target body is encountered at the planned distance and on the proper trajectory.
Between 1959 and 1971, NASA spacecraft were dispatched to study the Moon and the solar environment; they also scanned the inner planets other than Earth -- Mercury, Venus and Mars. These three worlds, and our own, are known as the terrestrial planets because they share a solid-rock composition.
For the early planetary reconnaissance missions, NASA employed a highly successful series of spacecraft called the Mariners. Their flights helped shape the planning of later missions. Between 1962 and 1975, seven Mariner missions conducted the first surveys of our planetary neighbors in space.
All of the Mariners used solar panels as their primary power source. The first and the final versions of the spacecraft had two wings covered with photovoltaic cells. Other Mariners were equipped with four solar panels extending from their octagonal bodies.
Although the Mariners ranged from the Mariner 2 Venus spacecraft, weighing in at 203 kilograms (447 pounds), to the Mariner 9 Mars Orbiter, weighing in at 974 kilograms (2,147 pounds), their basic design remained quite similar throughout the program. The Mariner 5 Venus spacecraft, for example, had originally been a backup for the Mariner 4 Mars flyby. The Mariner 10 spacecraft sent to Venus and Mercury used components left over from the Mariner 9 Mars Orbiter program.
In 1972, NASA launched Pioneer 10, a Jupiter spacecraft. Interest was shifting to four of the outer planets -- Jupiter, Saturn, Uranus and Neptune -- giant balls of dense gas quite different from the terrestrial worlds we had already surveyed.
Four NASA spacecraft in all -- two Pioneers and two Voyagers -- were sent in the 1970s to tour the outer regions of our solar system. Because of the distances involved, these travelers took anywhere from 20 months to 12 years to reach their destinations. Barring faster spacecraft, they will eventually become the first human artifacts to journey to distant stars. Because the Sun's light becomes so faint in the outer solar system, these travelers do not use solar power but instead operate on electricity generated by heat from the decay of radioisotopes.
NASA also developed highly specialized spacecraft to revisit our neighbors Mars and Venus in the middle and late 1970s. Twin Viking Landers were equipped to serve as seismic and weather stations and as biology laboratories. Two advanced orbiters -- descendants of the Mariner craft -- carried the Viking Landers from Earth and then studied martian features from above.
Two drum-shaped Pioneer spacecraft visited Venus in 1978. The Pioneer Venus Orbiter was equipped with a radar instrument that allowed it to "see" through the planet's dense cloud cover to study surface features. The Pioneer Venus Multiprobe carried four probes that were dropped through the clouds. The probes and the main body -- all of which contained scientific instruments -- radioed information about the planet's atmosphere during their descent toward the surface.
A new generation of automated spacecraft -- including Magellan, Galileo, Ulysses, Mars Observer and Cassini -- is being developed and sent out into the solar system to make detailed examinations that will increase our understanding of our neighborhood and our own planet.
THE SUN
A discussion of the objects in the solar system must start with the Sun. The Sun dwarfs the other bodies, representing approximately 99.86 percent of all the mass in the solar system; all of the planets, moons, asteroids, comets, dust and gas add up to only about 0.14 percent. This 0.14 percent represents the material left over from the Sun's formation. One hundred and nine Earths would be required to fit across the Sun's disk, and its interior could hold over 1.3 million Earths.
As a star, the Sun generates energy through the process of fusion. The temperature at the Sun's core is 15 million degrees Celsius (27 million degrees Fahrenheit), and the pressure there is 340 billion times Earth's air pressure at sea level. The Sun's surface temperature of 5,500 degrees Celsius (10,000 degrees Fahrenheit) seems almost chilly compared to its core-temperature. At the solar core, hydrogen can fuse into helium, producing energy. The Sun also produces a strong magnetic field and streams of charged particles, both extending far beyond the planets.
The Sun appears to have been active for 4.6 billion years and has enough fuel to go on for another five billion years or so. At the end of its life, the Sun will start to fuse helium into heavier elements and begin to swell up, ultimately growing so large that it will swallow Earth. After a billion years as a "red giant," it will suddenly collapse into a "white dwarf" -- the final end product of a star like ours. It may take a trillion years to cool off completely.
Many spacecraft have explored the Sun's environment, but none have gotten any closer to its surface than approximately two- thirds of the distance from Earth to the Sun. Pioneers 5-11, the Pioneer Venus Orbiter, Voyagers 1 and 2 and other spacecraft have all sampled the solar environment. The Ulysses spacecraft, launched on October 6, 1990, is a joint solar mission of NASA and the European Space Agency. On February 8, 1992, Ulysses flew close to Jupiter and used Jupiter's gravity to hurl it down below the plane of the planets. Although it was still a great distance from the Sun, Ulysses flew over the Sun's polar regions during 1994 and 1995 and performed a wide range of studies using nine onboard scientific instruments.
We are fortunate that the Sun is exactly the way it is. If it were different in almost any way, life would almost certainly never have developed on Earth.
MERCURY
Obtaining the first close-up views of Mercury was the primary objective of the Mariner 10 spacecraft, launched on November 3, 1973, from Kennedy Space Center in Florida. After a journey of nearly five months, which included a flyby of Venus, the spacecraft passed within 703 kilometers (437 miles) of the solar system's innermost planet on March 29, 1974.
Until Mariner 10, little was known about Mercury. Even the best telescopic views from Earth showed Mercury as an indistinct object lacking any surface detail. The planet is so close to the Sun that it is usually lost in solar glare. When the planet is visible on Earth's horizon just after sunset or before dawn, it is obscured by the haze and dust in our atmosphere. Only radar telescopes gave any hint of Mercury's surface conditions prior to the voyage of Mariner 10.
The photographs Mariner 10 radioed back to Earth revealed an ancient, heavily cratered surface, closely resembling our own Moon. The pictures also showed huge cliffs crisscrossing the planet. These apparently were created when Mercury's interior cooled and shrank, buckling the planet's crust. The cliffs are as high as 3 kilometers (2 miles) and as long as 500 kilometers (310 miles).
Instruments on Mariner 10 discovered that Mercury has a weak magnetic field and a trace of atmosphere -- a trillionth the density of Earth's atmosphere and composed chiefly of argon, neon and helium. When the planet's orbit takes it closest to the Sun, surface temperatures range from 467 degrees Celsius (872 degrees Fahrenheit) on Mercury's sunlit side to -183 degrees Celsius (-298 degrees Fahrenheit) on the dark side. This range in surface temperature -- 650 degrees Celsius (1,170 degrees Fahrenheit) -- is the largest for a single body in the solar system. Mercury literally bakes and freezes at the same time.
Days and nights are long on Mercury. The combination of a slow rotation relative to the stars (59 Earth days) and a rapid revolution around the Sun (88 Earth days) means that one Mercury solar day takes 176 Earth days or two Mercury years -- the time it takes the innermost planet to complete two orbits around the Sun!
Mercury appears to have a crust of light silicate rock like that of Earth. Scientists believe Mercury has a heavy iron-rich core making up slightly less than half of its volume. That would make Mercury's core larger, proportionally, than the Moon's core or those of any of the planets.
After the initial Mercury encounter, Mariner 10 made two additional flybys -- on September 21, 1974, and March 16, 1975 -- before control gas used to orient the spacecraft was exhausted and the mission was concluded. Each flyby took place at the same local Mercury time when the identical half of the planet was illuminated; as a result, we still have not seen one-half of the planet's surface.
VENUS
Veiled by dense cloud cover, Venus -- our nearest planetary neighbor -- was the first planet to be explored. The Mariner 2 spacecraft, launched on August 27, 1962, was the first of more than a dozen successful American and Soviet missions to study the mysterious planet. As spacecraft flew by or orbited Venus, plunged into the atmosphere or gently landed on Venus' surface, romantic myths and speculations about our neighbor were laid to rest.
On December 14, 1962, Mariner 2 passed within 34,839 kilometers (21,648 miles) of Venus and became the first spacecraft to scan another planet; onboard instruments measured Venus for 42 minutes. Mariner 5, launched in June 1967, flew much closer to the planet. Passing within 4,094 kilometers (2,544 miles) of Venus on the second American flyby, Mariner 5's instruments measured the planet's magnetic field, ionosphere, radiation belts and temperatures. On its way to Mercury, Mariner 10 flew by Venus and transmitted ultraviolet pictures to Earth showing cloud circulation patterns in the Venusian atmosphere.
In the spring and summer of 1978, two spacecraft were launched to further unravel the mysteries of Venus. On December 4 of the same year, the Pioneer Venus Orbiter became the first spacecraft placed in orbit around the planet.
Five days later, the five separate components making up the second spacecraft -- the Pioneer Venus Multiprobe -- entered the Venusian atmosphere at different locations above the planet. The four small, independent probes and the main body radioed atmospheric data back to Earth during their descent toward the surface. Although designed to examine the atmosphere, one of the probes survived its impact with the surface and continued to transmit data for another hour.
Venus resembles Earth in size, physical composition and density more closely than any other known planet. However, spacecraft have discovered significant differences as well. For example, Venus' rotation (west to east) is retrograde (backward) compared to the east-to-west spin of Earth and most of the other planets.
Approximately 96.5 percent of Venus' atmosphere (95 times as dense as Earth's) is carbon dioxide. The principal constituent of Earth's atmosphere is nitrogen. Venus' atmosphere acts like a greenhouse, permitting solar radiation to reach the surface but trapping the heat that would ordinarily be radiated back into space. As a result, the planet's average surface temperature is 482 degrees Celsius (900 degrees Fahrenheit), hot enough to melt lead.
A radio altimeter on the Pioneer Venus Orbiter provided the first means of seeing through the planet's dense cloud cover and determining surface features over almost the entire planet. NASA's Magellan spacecraft, launched on May 5, 1989, has been in orbit around Venus since August 10, 1990. The spacecraft used radar- mapping techniques to provide high-resolution images of 98 percent of the surface.
Magellan's radar revealed a landscape dominated by volcanic features, faults and impact craters. Huge areas of the surface show evidence of multiple periods of lava flooding with flows lying on top of previous ones. An elevated region named Ishtar Terra is a lava-filled basin as large as the United States. At one end of this plateau sits Maxwell Montes, a mountain the size of Mount Everest. Scarring the mountain's flank is a 100-kilometer (62-mile) wide, 2.5-kilometer (1.5-mile) deep impact crater named Cleopatra. (Almost all features on Venus are named for women; Maxwell Montes, Alpha Regio and Beta Regio are the exceptions.) Craters survive on Venus for perhaps 400 million years because there is no water and very little wind erosion.
Extensive fault-line networks cover the planet, probably the result of the same crustal flexing that produces plate tectonics on Earth. But on Venus the surface temperature is sufficient to weaken the rock, which cracks just about everywhere, preventing the formation of major plates and large earthquake faults like the San Andreas Fault in California.
Venus' predominant weather pattern is a high-altitude, high-speed circulation of clouds that contain sulfuric acid. At speeds reaching as high as 360 kilometers (225 miles) per hour, the clouds circle the planet in only four Earth days. The circulation is in the same direction -- west to east -- as Venus' slow rotation of 243 Earth days, whereas Earth's winds blow in both directions -- west to east and east to west -- in six alternating bands. Venus' atmosphere serves as a simplified laboratory for the study of our weather.
EARTH
As viewed from space, our world's distinguishing characteristics are its blue waters, brown and green land masses and white clouds. We are enveloped by an ocean of air consisting of 78 percent nitrogen, 21 percent oxygen and 1 percent other constituents. The only planet in the solar system known to harbor life, Earth orbits the Sun at an average distance of 150 million kilometers (93 million miles). Earth is the third planet from the Sun and the fifth largest in the solar system, with a diameter just a few hundred kilometers larger than that of Venus.
Our planet's rapid spin and molten nickel-iron core give rise to an extensive magnetic field, which, along with the atmosphere, shields us from nearly all of the harmful radiation coming from the Sun and other stars. Earth's atmosphere protects us from meteors as well, most of which burn up before they can strike the surface. Active geological processes have left no evidence of the pelting Earth almost certainly received soon after it formed -- about 4.6 billion years ago. Along with the other newly formed planets, it was showered by space debris in the early days of the solar system.
From our journeys into space, we have learned much about our home planet. The first American satellite -- Explorer 1 -- was launched from Cape Canaveral in Florida on January 31, 1958, and discovered an intense radiation zone, now called the Van Allen radiation belts, surrounding Earth.
Since then, other research satellites have revealed that our planet's magnetic field is distorted into a tear-drop shape by the solar wind -- the stream of charged particles continuously ejected from the Sun. We've learned that the magnetic field does not fade off into space but has definite boundaries. And we now know that our wispy upper atmosphere, once believed calm and uneventful, seethes with activity -- swelling by day and contracting by night. Affected by changes in solar activity, the upper atmosphere contributes to weather and climate on Earth.
Besides affecting Earth's weather, solar activity gives rise to a dramatic visual phenomenon in our atmosphere. When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles. These air molecules then begin to glow and are known as the auroras or the northern and southern lights.
Satellites about 35,789 kilometers (22,238 miles) out in space play a major role in daily local weather forecasting. These watchful electronic eyes warn us of dangerous storms. Continuous global monitoring provides a vast amount of useful data and contributes to a better understanding of Earth's complex weather systems.
From their unique vantage points, satellites can survey Earth's oceans, land use and resources, and monitor the planet's health. These eyes in space have saved countless lives, provided tremendous conveniences and shown us that we may be altering our planet in dangerous ways.
THE MOON
The Moon is Earth's single natural satellite. The first human footsteps on an alien world were made by American astronauts on the dusty surface of our airless, lifeless companion. In preparation for the human-crewed Apollo expeditions, NASA dispatched the automated Ranger, Surveyor and Lunar Orbiter spacecraft to study the Moon between 1964 and 1968.
NASA's Apollo program left a large legacy of lunar materials and data. Six two-astronaut crews landed on and explored the lunar surface between 1969 and 1972, carrying back a collection of rocks and soil weighing a total of 382 kilograms (842 pounds) and consisting of more than 2,000 separate samples.
From this material and other studies, scientists have constructed a history of the Moon that includes its infancy. Rocks collected from the lunar highlands date to about 4.0-4.3 billion years old. The first few million years of the Moon's existence were so violent that few traces of this period remain. As a molten outer layer gradually cooled and solidified into different kinds of rock, the Moon was bombarded by huge asteroids and smaller objects. Some of the asteroids were as large as Rhode Island or Delaware, and their collisions with the Moon created basins hundreds of kilometers across.
This catastrophic bombardment tapered off approximately four billion years ago, leaving the lunar highlands covered with huge, overlapping craters and a deep layer of shattered and broken rock. Heat produced by the decay of radioactive elements began to melt the interior of the Moon at depths of about 200 kilometers (125 miles) below the surface. Then, for the next 700 million years -- from about 3.8 to 3.1 billion years ago -- lava rose from inside the Moon. The lava gradually spread out over the surface, flooding the large impact basins to form the dark areas that Galileo Galilei, an astronomer of the Italian Renaissance, called maria, meaning seas.
As far as we can tell, there has been no significant volcanic activity on the Moon for more than three billion years. Since then, the lunar surface has been altered only by micrometeorites, by the atomic particles from the Sun and stars, by the rare impacts of large meteorites and by spacecraft and astronauts. If our astronauts had landed on the Moon a billion years ago, they would have seen a landscape very similar to the one today. Thousands of years from now, the footsteps left by the Apollo crews will remain sharp and clear.
The origin of the Moon is still a mystery. Four theories attempt an explanation: the Moon formed near Earth as a separate body; it was torn from Earth; it formed somewhere else and was captured by our planet's gravity, or it was the result of a collision between Earth and an asteroid about the size of Mars. The last theory has some good support but is far from certain.
MARS
Of all the planets, Mars has long been considered the solar system's prime candidate for harboring extraterrestrial life. Astronomers studying the red planet through telescopes saw what appeared to be straight lines crisscrossing its surface. These observations -- later determined to be optical illusions -- led to the popular notion that intelligent beings had constructed a system of irrigation canals on the planet. In 1938, when Orson Welles broadcast a radio drama based on the science fiction classic War of the Worlds by H.G. Wells, enough people believed in the tale of invading martians to cause a near panic.
Another reason for scientists to expect life on Mars had to do with the apparent seasonal color changes on the planet's surface. This phenomenon led to speculation that conditions might support a bloom of martian vegetation during the warmer months and cause plant life to become dormant during colder periods.
So far, six American missions to Mars have been carried out. Four Mariner spacecraft -- three flying by the planet and one placed into martian orbit -- surveyed the planet extensively before the Viking Orbiters and Landers arrived.
Mariner 4, launched in late 1964, flew past Mars on July 14, 1965, coming within 9,846 kilometers (6,118 miles) of the surface. Transmitting to Earth 22 close-up pictures of the planet, the spacecraft found many craters and naturally occurring channels but no evidence of artificial canals or flowing water. Mariners 6 and 7 followed with their flybys during the summer of 1969 and returned 201 pictures. Mariners 4, 6 and 7 showed a diversity of surface conditions as well as a thin, cold, dry atmosphere of carbon dioxide.
On May 30, 1971, the Mariner 9 Orbiter was launched on a mission to make a year-long study of the martian surface. The spacecraft arrived five and a half months after lift-off, only to find Mars in the midst of a planet-wide dust storm that made surface photography impossible for several weeks. But after the storm cleared, Mariner 9 began returning the first of 7,329 pictures; these revealed previously unknown martian features, including evidence that large amounts of water once flowed across the surface, etching river valleys and flood plains.
In August and September 1975, the Viking 1 and 2 spacecraft -- each consisting of an orbiter and a lander -- lifted off from Kennedy Space Center. The mission was designed to answer several questions about the red planet, including, Is there life there? Nobody expected the spacecraft to spot martian cities, but it was hoped that the biology experiments on the Viking Landers would at least find evidence of primitive life -- past or present.
Viking Lander 1 became the first spacecraft to successfully touch down on another planet when it landed on July 20, 1976, while the United States was celebrating its Bicentennial. Photos sent back from the Chryse Planitia ("Plains of Gold") showed a bleak, rusty-red landscape. Panoramic images returned by the lander revealed a rolling plain, littered with rocks and marked by rippled sand dunes. Fine red dust from the Martian soil gives the sky a salmon hue. When Viking Lander 2 touched down on Utopia Planitia on September 3, 1976, it viewed a more rolling landscape than the one seen by its predecessor -- one without visible dunes.
The results sent back by the laboratory on each Viking Lander were inconclusive. Small samples of the red Martian soil were tested in three different experiments designed to detect biological processes. While some of the test results seemed to indicate biological activity, later analysis confirmed that this activity was inorganic in nature and related to the planet's soil chemistry. Is there life on Mars? No one knows for sure, but the Viking mission found no evidence that organic molecules exist there.
The Viking Landers became weather stations, recording wind velocity and direction as well as atmospheric temperature and pressure. Few weather changes were observed. The highest temperature recorded by either craft was -14 degrees Celsius (7 degrees Fahrenheit) at the Viking Lander 1 site in midsummer.
The lowest temperature, -120 degrees Celsius (-184 degrees Fahrenheit), was recorded at the more northerly Viking Lander 2 site during winter. Near-hurricane wind speeds were measured at the two martian weather stations during global dust storms, but because the atmosphere is so thin, wind force is minimal. Viking Lander 2 photographed light patches of frost -- probably water-ice -- during its second winter on the planet.
The martian atmosphere, like that of Venus, is primarily carbon dioxide. Nitrogen and oxygen are present only in small percentages. Martian air contains only about 1/1,000 as much water as our air, but even this small amount can condense out, forming clouds that ride high in the atmosphere or swirl around the slopes of towering volcanoes. Local patches of early morning fog can form in valleys.
There is evidence that in the past a denser martian atmosphere may have allowed water to flow on the planet. Physical features closely resembling shorelines, gorges, riverbeds and islands suggest that great rivers once marked the planet.
Mars has two moons, Phobos and Deimos. They are small and irregularly shaped and possess ancient, cratered surfaces. It is possible the moons were originally asteroids that ventured too close to Mars and were captured by its gravity.
The Viking Orbiters and Landers exceeded by large margins their design lifetimes of 120 and 90 days, respectively. The first to fail was Viking Orbiter 2, which stopped operating on July 24, 1978, when a leak depleted its attitude-control gas. Viking Lander 2 operated until April 12, 1980, when it was shut down because of battery degeneration. Viking Orbiter 1 quit on August 7, 1980, when the last of its attitude-control gas was used up. Viking Lander 1 ceased functioning on November 13, 1983.
Despite the inconclusive results of the Viking biology experiments, we know more about Mars than any other planet except Earth. NASA's Mars Observer and Mars Pathfinder/Sojourner spacecraft expanded our knowledge of the martian environment and future missions to Mars will help lead to human exploration of the red planet.
ASTEROIDS
The solar system has a large number of rocky and metallic objects that are in orbit around the Sun but are too small to be considered full-fledged planets. These objects are known as asteroids or minor planets. Most, but not all, are found in a band or belt between the orbits of Mars and Jupiter. Some have orbits that cross Earth's path, and there is evidence that Earth has been hit by asteroids in the past. One of the least eroded, best preserved examples is the Barringer Meteor Crater near Winslow, Arizona.
Asteroids are material left over from the formation of the solar system. One theory suggests that they are the remains of a planet that was destroyed in a massive collision long ago. More likely, asteroids are material that never coalesced into a planet. In fact, if the estimated total mass of all asteroids was gathered into a single object, the object would be less than 1,500 kilometers (932 miles) across -- less than half the diameter of our Moon.
Thousands of asteroids have been identified from Earth. It is estimated that 100,000 are bright enough to eventually be photographed through Earth-based telescopes.
Much of our understanding about asteroids comes from examining pieces of space debris that fall to the surface of Earth. Asteroids that are on a collision course with Earth are called meteoroids. When a meteoroid strikes our atmosphere at high velocity, friction causes this chunk of space matter to incinerate in a streak of light known as a meteor. If the meteoroid does not burn up completely, what's left strikes Earth's surface and is called a meteorite. One of the best places to look for meteorites is the ice cap of Antarctica.
Of all the meteorites examined, 92.8 percent are composed of silicate (stone), and 5.7 percent are composed of iron and nickel; the rest are a mixture of the three materials. Stony meteorites are the hardest to identify since they look very much like terrestrial rocks.
Since asteroids are material from the very early solar system, scientists are interested in their composition. Spacecraft that have flown through the asteroid belt have found that the belt is really quite empty and that asteroids are separated by very large distances.
Current and future missions will fly by selected asteroids for closer examination. The Galileo spacecraft, launched by NASA in October 1989, investigated the main-belt asteroid Gaspra on October 29, 1991 and will encounter Ida on August 28, 1993 on its way to Jupiter. One day, space factories will mine the asteroids for raw materials.
JUPITER
Beyond Mars and the asteroid belt, in the outer regions of our solar system, lie the giant planets of Jupiter, Saturn, Uranus and Neptune. In 1972, NASA dispatched the first of four spacecraft slated to conduct the initial surveys of these colossal worlds of gas and their moons of ice and rock. Jupiter was the first port of call.
Pioneer 10, which lifted off from Kennedy Space Center in March 1972, was the first spacecraft to penetrate the asteroid belt and travel to the outer regions of the solar system. In December 1973, it returned the first close-up images of Jupiter, flying within 132,252 kilometers (82,178 miles) of the planet's banded cloud tops. Pioneer 11 followed a year later. Voyagers 1 and 2 were launched in the summer of 1977 and returned spectacular photographs of Jupiter and its family of satellites during flybys in 1979.
These travelers found Jupiter to be a whirling ball of liquid hydrogen and helium, topped with a colorful atmosphere composed mostly of gaseous hydrogen and helium. Ammonia ice crystals form white Jovian clouds. Sulfur compounds (and perhaps phosphorus) may produce the brown and orange hues that characterize Jupiter's atmosphere.
It is likely that methane, ammonia, water and other gases react to form organic molecules in the regions between the planet's frigid cloud tops and the warmer hydrogen ocean lying below. Because of Jupiter's atmospheric dynamics, however, these organic compounds -- if they exist -- are probably short-lived.
The Great Red Spot has been observed for centuries through telescopes on Earth. This hurricane-like storm in Jupiter's atmosphere is more than twice the size of our planet. As a high-pressure region, the Great Red Spot spins in a direction opposite to that of low-pressure storms on Jupiter; it is surrounded by swirling currents that rotate around the spot and are sometimes consumed by it. The Great Red Spot might be a million years old.
Our spacecraft detected lightning in Jupiter's upper atmosphere and observed auroral emissions similar to Earth's northern lights at the Jovian polar regions. Voyager 1 returned the first images of a faint, narrow ring encircling Jupiter.
Largest of the solar system's planets, Jupiter rotates at a dizzying pace -- once every 9 hours 55 minutes 30 seconds. The massive planet takes almost 12 Earth years to complete a journey around the Sun. With 16 known moons, Jupiter is something of a miniature solar system.
A new mission to Jupiter -- the Galileo Project -- is under way. On December 7, 1995, after a six- year cruise that takes the Galileo Orbiter once past Venus, twice past Earth and the Moon and once past two asteroids, the spacecraft will drop an atmospheric probe into Jupiter's cloud layers and relay data back to Earth. The Galileo Orbiter will spend two years circling the planet and flying close to Jupiter's large moons, exploring in detail what the two Pioneers and two Voyagers revealed.
GALILEAN SATELLITES
In 1610, Galileo Galilei aimed his telescope at Jupiter and spotted four points of light orbiting the planet. For the first time, humans had seen the moons of another world. In honor of their discoverer, these four bodies would become known as the Galilean satellites or moons. But Galileo might have happily traded this honor for one look at the dazzling photographs returned by the Voyager spacecraft as they flew past these planet- sized satellites.
One of the most remarkable findings of the Voyager mission was the presence of active volcanoes on the Galilean moon Io. Volcanic eruptions had never before been observed on a world other than Earth. The Voyager cameras identified at least nine active volcanoes on Io, with plumes of ejected material extending as far as 280 kilometers (175 miles) above the moon's surface.
Io's pizza-colored terrain, marked by orange and yellow hues, is probably the result of sulfur-rich materials brought to the surface by volcanic activity. Volcanic activity on this satellite is the result of tidal flexing caused by the gravitational tug-of- war between Io, Jupiter and the other three Galilean moons.
Europa, approximately the same size as our Moon, is the brightest Galilean satellite. The moon's surface displays a complex array of streaks, indicating the crust has been fractured. Caught in a gravitational tug-of-war like Io, Europa has been heated enough to cause its interior ice to melt -- apparently producing a liquid-water ocean. This ocean is covered by an ice crust that has formed where water is exposed to the cold of space. Europa's core is made of rock that sank to its center.
Like Europa, the other two Galilean moons -- Ganymede and Callisto -- are worlds of ice and rock. Ganymede is the largest satellite in the solar system -- larger than the planets Mercury and Pluto. The satellite is composed of about 50 percent ice or slush and the rest rock. Ganymede's surface has areas of different brightness, indicating that, in the past, material oozed out of the moon's interior and was deposited at various locations on the surface.
Callisto, only slightly smaller than Ganymede, has the lowest density of any Galilean satellite, suggesting that large amounts of water are part of its composition. Callisto is the most heavily cratered object in the solar system; no activity during its history has erased old craters except more impacts.
Detailed studies of all the Galilean satellites will be performed by the Galileo Orbiter.
SATURN
No planet in the solar system is adorned like Saturn. Its exquisite ring system is unrivaled. Like Jupiter, Saturn is composed mostly of hydrogen. But in contrast to the vivid colors and wild turbulence found in Jovian clouds, Saturn's atmosphere has a more subtle, butterscotch hue, and its markings are muted by high-altitude haze. Given Saturn's somewhat placid-looking appearance, scientists were surprised at the high-velocity equatorial jet stream that blows some 1,770 kilometers (1,100 miles) per hour.
Three American spacecraft have visited Saturn. Pioneer 11 sped by the planet and its moon Titan in September 1979, returning the first close-up images. Voyager 1 followed in November 1980, sending back breathtaking photographs that revealed for the first time the complexities of Saturn's ring system and moons. Voyager 2 flew by the planet and its moons in August 1981.
The rings are composed of countless low-density particles orbiting individually around Saturn's equator at progressive distances from the cloud tops. Analysis of spacecraft radio waves passing through the rings showed that the particles vary widely in size, ranging from dust to house-sized boulders. The rings are bright because they are mostly ice and frosted rock.
The rings might have resulted when a moon or a passing body ventured too close to Saturn. The unlucky object would have been torn apart by great tidal forces on its surface and in its interior. Or the object may not have been fully formed to begin with and disintegrated under the influence of Saturn's gravity. A third possibility is that the object was shattered by collisions with larger objects orbiting the planet.
Unable either to form into a moon or to drift away from each other, individual ring particles appear to be held in place by the gravitational pull of Saturn and its satellites. These complex gravitational interactions form the thousands of ringlets that make up the major rings.
Radio emissions quite similar to the static heard on an AM car radio during an electrical storm were detected by the Voyager spacecraft. These emissions are typical of lightning but are believed to be coming from Saturn's ring system rather than its atmosphere, where no lightning was observed. As they had at Jupiter, the Voyagers saw a version of Earth's auroras near Saturn's poles.
The Voyagers discovered new moons and found several satellites that share the same orbit. We learned that some moons shepherd ring particles, maintaining Saturn's rings and the gaps in the rings. Saturn's 18th moon was discovered in 1990 from images taken by Voyager 2 in 1981.
Voyager 1 determined that Titan has a nitrogen-based atmosphere with methane and argon -- one more like Earth's in composition than the carbon dioxide atmospheres of Mars and Venus. Titan's surface temperature of -179 degrees Celsius (-290 degrees Fahrenheit) implies that there might be water-ice islands rising above oceans of ethane-methane liquid or sludge. Unfortunately, Voyager's cameras could not penetrate the moon's dense clouds.
Continuing photochemistry from solar radiation may be converting Titan's methane to ethane, acetylene and -- in combination with nitrogen -- hydrogen cyanide. The latter compound is a building block of amino acids. These conditions may be similar to the atmospheric conditions of primeval Earth between three and four billion years ago. However, Titan's atmospheric temperature is believed to be too low to permit progress beyond this stage of organic chemistry.
The exploration of Saturn will continue with the Cassini mission. Scheduled for launch in the latter part of the 1990s, the Cassini mission is a collaborative project of NASA, the European Space Agency and the federal space agencies of Italy and Germany, as well as the United States Air Force and the Department of Energy. Cassini will orbit the planet and will also deploy a probe called Huygens, which will be dropped into Titan's atmosphere and fall to the surface. Cassini will use radar to peer through Titan's clouds and will spend years examining the Saturnian system.
URANUS
In January 1986, four and a half years after visiting Saturn, Voyager 2 completed the first close-up survey of the Uranian system. The brief flyby revealed more information about Uranus and its retinue of icy moons than had been gleaned from ground observations since the planet's discovery over two centuries ago by the English astronomer William Herschel.
Uranus, third largest of the planets, is an oddball of the solar system. Unlike the other planets (with the exception of Pluto), this giant lies tipped on its side with its north and south poles alternately facing the sun during an 84-year swing around the solar system. During Voyager 2's flyby, the south pole faced the Sun. Uranus might have been knocked over when an Earth- sized object collided with it early in the life of the solar system.
Voyager 2 found that Uranus' magnetic field does not follow the usual north-south axis found on the other planets. Instead, the field is tilted 60 degrees and offset from the planet's center, a phenomenon that on Earth would be like having one magnetic pole in New York City and the other in the city of Djakarta, on the island of Java in Indonesia.
Uranus' atmosphere consists mainly of hydrogen, with some 12 percent helium and small amounts of ammonia, methane and water vapor. The planet's blue color occurs because methane in its atmosphere absorbs all other colors. Wind speeds range up to 580 kilometers (360 miles) per hour, and temperatures near the cloud tops average -221 degrees Celsius (-366 degrees Fahrenheit).
Uranus' sunlit south pole is shrouded in a kind of photochemical "smog" believed to be a combination of acetylene, ethane and other sunlight-generated chemicals. Surrounding the planet's atmosphere and extending thousands of kilometers into space is a mysterious ultraviolet sheen known as "electroglow."
Approximately 8,000 kilometers (5,000 miles) below Uranus' cloud tops, there is thought to be a scalding ocean of water and dissolved ammonia some 10,000 kilometers (6,200 miles) deep. Beneath this ocean is an Earth-sized core of heavier materials.
Voyager 2 discovered 10 new moons, 16-169 kilometers (10-105 miles) in diameter, orbiting Uranus. The five previously known -- Miranda, Ariel, Umbriel, Titania and Oberon -- range in size from 520 to 1,610 kilometers (323 to 1,000 miles) across. Representing a geological showcase, these five moons are half-ice, half-rock spheres that are cold and dark and show evidence of past activity, including faulting and ice flows.
The most remarkable of Uranus' moons is Miranda. Its surface features high cliffs as well as canyons, crater-pocked plains and winding valleys. The sharp variations in terrain suggest that, after the moon formed, it was smashed apart by a collision with another body -- an event not unusual in our solar system, which contains many objects that have impact craters or are fragments from large impacts. What is extraordinary is that Miranda apparently reformed with some of the material that had been in its interior exposed on its surface.
Uranus was thought to have nine dark rings; Voyager 2 imaged 11. In contrast to Saturn's rings, which are composed of bright particles, Uranus' rings are primarily made up of dark, boulder- sized chunks.
NEPTUNE
Voyager 2 completed its 12-year tour of the solar system with an investigation of Neptune and the planet's moons. On August 25, 1989, the spacecraft swept to within 4,850 kilometers (3,010 miles) of Neptune and then flew on to the moon Triton. During the Neptune encounter it became clear that the planet's atmosphere was more active than Uranus'.
Voyager 2 observed the Great Dark Spot, a circular storm the size of Earth, in Neptune's atmosphere. Resembling Jupiter's Great Red Spot, the storm spins counterclockwise and moves westward at almost 1,200 kilometers (745 miles) per hour. Voyager 2 also noted a smaller dark spot and a fast-moving cloud dubbed the "Scooter," as well as high-altitude clouds over the main hydrogen and helium cloud deck. The highest wind speeds of any planet were observed, up to 2,400 kilometers (1,500 miles) per hour.
Like the other giant planets, Neptune has a gaseous hydrogen and helium upper layer over a liquid interior. The planet's core contains a higher percentage of rock and metal than those of the other gas giants. Neptune's distinctive blue appearance, like Uranus' blue color, is due to atmospheric methane.
Neptune's magnetic field is tilted relative to the planet's spin axis and is not centered at the core. This phenomenon is similar to Uranus' magnetic field and suggests that the fields of the two giants are being generated in an area above the cores, where the pressure is so great that liquid hydrogen assumes the electrical properties of a metal. Earth's magnetic field, on the other hand, is produced by its spinning metallic core and is only slightly tilted and offset relative to its center.
Voyager 2 also shed light on the mystery of Neptune's rings. Observations from Earth indicated that there were arcs of material in orbit around the giant planet. It was not clear how Neptune could have arcs and how these could be kept from spreading out into even, unclumped rings. Voyager 2 detected these arcs, but they were, in fact, part of thin, complete rings. A number of small moons could explain the arcs, but such bodies were not spotted.
Astronomers had identified the Neptunian moons Triton in 1846 and Nereid in 1949. Voyager 2 found six more. One of the new moons -- Proteus -- is actually larger than Nereid, but since Proteus orbits close to Neptune, it was lost in the planet's glare for observers on Earth.
Triton circles Neptune in a retrograde orbit in under six days. Tidal forces on Triton are causing it to spiral slowly towards the planet. In 10 to 100 million years (a short time in astronomical terms), the moon will be so close that Neptunian gravity will tear it apart, forming a spectacular ring to accompany the planet's modest current rings.
Triton's landscape is as strange and unexpected as those of Io and Miranda. The moon has more rock than its counterparts at Saturn and Uranus. Triton's mantle is probably composed of water- ice, but the moon's crust is a thin veneer of nitrogen and methane. The moon shows two dramatically different types of terrain: the so-called "cantaloupe" terrain and a receding ice cap.
Dark streaks appear on the ice cap. These streaks are the fallout from geyser-like volcanic vents that shoot nitrogen gas and dark, fine-grained particles to heights of 2 to 8 kilometers (1 to 5 miles). Triton's thin atmosphere, only 1/70,000th as thick as Earth's, has winds that carry the dark particles and deposit them as streaks on the ice cap -- the coldest surface yet found in the solar system (-235 degrees Celsius, -391 degrees Fahrenheit). Triton might be more like Pluto than any other object spacecraft have so far visited.
PLUTO
Pluto is the most distant of the planets, yet the eccentricity of its orbit periodically carries it inside Neptune's orbit, where it has been since 1979 and where it will remain until March 1999. Pluto's orbit is also highly inclined -- tilted 17 degrees to the orbital plane of the other planets.
Discovered in 1930, Pluto appears to be little more than a celestial snowball. The planet's diameter is calculated to be approximately 2,300 kilometers (1,430 miles), only two-thirds the size of our Moon. Ground-based observations indicate that Pluto's surface is covered with methane ice and that there is a thin atmosphere that may freeze and fall to the surface as the planet moves away from the Sun. Observations also show that Pluto's spin axis is tipped by 122 degrees.
The planet has one known satellite, Charon, discovered in 1978. Charon's surface composition is different from Pluto's: the moon appears to be covered with water-ice rather than methane ice. Its orbit is gravitationally locked with Pluto, so both bodies always keep the same hemisphere facing each other. Pluto's and Charon's rotational period and Charon's period of revolution are all 6.4 Earth days.
Although no spacecraft have ever visited Pluto, NASA is currently exploring the possibility of such a mission.
Constellation Photos and Outlines
Andromeda, the Princess
Andromeda was the princess of Ethiopia, daughter of Cepheus and Cassiopeia. Cassiopeia was a boastful woman, and foolishly bragged that she was more beautiful than Juno, the queen of the gods, and the Nereids. In order to avenge the insult to his nymphs, Neptune sent a sea monster to ravage the Ethiopian coast. (Some accounts state that the constellation Cetus represents the sea monster, but a more common view of Cetus is that he is a peaceful whale.)
The horrified king consulted Ammon, the oracle of Jupiter, who said that Neptune could be appeased only by sacrificing Cassiopeia's beautiful virgin daughter, Andromeda, to the monster. Andromeda was duly chained to a rock on the coast, fully exposed to the monster. Fortunately for her, the hero Perseus happened to be flying by on his way back from killing the Gorgon Medusa:
When Perseus saw the princess, her arms chained to the hard rock, he would have taken her for a marble statue, had not the light breeze stirred her hair, and warm tears streamed from her eyes. Without realizing it, he fell in love. Amazed at the sight of such rare beauty, he stood still in wonder, and almost forgot to keep his wings moving in the air. As he came to a halt, he called out: "You should not be wearing such chains as these--the proper bonds for you are those which bind the hearts of fond lovers! Tell me your name, I pray, and the name of your country, and why you are in chains."
At first she was silent; for, being a girl, she did not dare to speak to a man. She would have concealed her face modestly behind her hands, had they not been bound fast. What she could do, she did, filling her eyes with starting tears. When Perseus persisted, questioning her again and again, she became afraid lest her unwillingness to talk might seem due to guilt; so she told him the name of her country, and her own name, and she also told him how her mother, a beautiful woman, had been too confident in her beauty.
Before she had finished, the waters roared and from the ocean wastes there came a menacing monster, its breast covering the waves far and wide. The girl screamed. Her sorrowing father was close at hand, and her mother too. They were both in deep distress, though the mother had more cause to be so (Metamorphoses IV 674-692)
Perseus says to Andromeda's parents that he'll kill the monster if they agree to give him their daughter's hand in marriage. They of course give him their consent, and Perseus kills the monster. (His exact method of doing so varies in different versions of the myth. Ovid has Perseus stab the monster to death after a drawn-out, bloody battle, while other versions have the hero simply hold up the head of Medusa, turning the monster to stone.) Andromeda is freed, and the two joyously marry.
Andromeda is represented in the sky as the figure of a woman with her arms outstreched and chained at the wrists.
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Aquarius, the Water Carrier
The water carrier represented by the zodiacal constellation Aquarius is Ganymede, a beautiful Phrygian youth. Ganymede was the son of Tros, king of Troy (according to Lucian, he was also son of Dardanus). While tending his father's flocks on Mount Ida, Ganymede was spotted by Jupiter. The king of gods became enamored of the boy and flew down to the mountain in the form of a large bird, whisking Ganymede away to the heavens. Ever since, the boy has served as cupbearer to the gods. Ovid has Orpheus sing the tale:
"The king of the gods was once fired with love for Phrygian Ganymede, and when that happened Jupiter found another shape preferable to his own. Wishing to turn himself into a bird, he none the less scorned to change into any save that which can carry his thunderbolts. Then without delay, beating the air on borrowed pinions, he snatched away the shepherd of Ilium, who even now mixes the winecups, and supplies Jove with nectar, to the annoyance of Juno" (Metamorphoses X 154-160).
Aquarius is a summer constellation in the northern hemisphere, found near Pisces and Cetus. It is especially notable as the radiant for four meteor showers, the largest of which is the Delta Aquarid meteor shower in late July and early August.
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Aquila, Servant of Zeus
Aquila, the celestial eagle, is one of the three constellations which have bright stars forming the Summer Triangle. A nearly perfectly straight line of three stars symbolizes part of the wings. The center and brightest of these three stars is Altair.
The tips of the wings extend further to the southeast and northwest. The head of the eagle stretches off to the southwest. A challenging open cluster can be found in Aquila, a few degrees southwest of the northernmost wingtip of the eagle. The stars in this cluster are so faint that they cannot be resolved with binoculars, but instead appear as only a light smudge.
Two dark nebulae form a shape known as "Fish on the Platter". They are located about 1.5 degrees west of the star just north of Altair. To the ancient Greeks, Aquila was the servant of Zeus who held the god's thunderbolts and performed errands for him.
He may also be the great eagle who devours Prometheus' liver as punishment for giving fire to humans. The line of three stars which includes Altair is revered by Indians as the footprints of the god Vishnu. Some Asian traditions see the bright star Vega as the Weaving-Princess star who marries a shepherd, the star Altair.
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Aries, the Ram
Aries is a zodiacal constellation representing the ram of the Golden Fleece sought by Jason and the Argonauts. The ram had originally been presented to Nephele by Mercury when her husband took a new wife, Ino, who persecuted Nephele's children.
To keep them safe, Nephele sent Phrixus and Helle away on the back of the magical ram, who flew away to the east. Helle fell off into the Hellespont (now the Dardanelles) between the Aegean Sea and the Sea of Marmara, but Phrixus safely made it to Colchis on the eastern shore of the Black Sea. Phrixus sacrificed the ram and presented the Golden Fleece to the king, Aeetes.
Roughly 2000 years ago, the vernal equinox was in the constellation Aries. This is no longer the case, due to precession of the earth's axis, but Aries is still regarded as the first constellation in the zodiac.
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Bootes, the Herdsman
Bootes, the herdsman, rides through the sky during the late Spring and early Summer. While he may have appeared as a shepherd to the ancients, modern star-gazers like us can easily recognize the shape of a kite, with the bright star Arcturus at the point of the kite where the tail is attached.
Arcturus is a bright red supergiant star with a diameter nearly 20 times that of the Sun and a brightness more than 100 times that of our Sun. Since it is only 36 light-years away (close for a star!), it appears as the brightest star in Bootes, and, in fact, the fourth brightest star in the sky. The name Bootes is derived from the Sumerian Riv-but-sane, which means the "man who drove the cart".
So Bootes was identified with a farmer who plows the land during spring. The Romans called Bootes the Herdsman of the Septemtriones, that is, of the seven oxen represented by the seven stars of the Big Dipper, which was seen as the cart or the plow.
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Cancer, the Crab
Cancer is a zodiacal constellation. Like many other constellations, its mythological importance is uncertain; however, the most widely accepted story is that Cancer was the crab sent to harass Hercules while he was on his second labor. As he battled the Lernaean Hydra, the ever-jealous Juno sent Cancer to nip at the hero's heels. The crab was eventually crushed beneath Hercules's feet, but Juno placed it in the heavens as a reward for its faithful service.
Cancer may be found between the constellations of Leo and Gemini.
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Capricornus, the Sea Goat
This zodiacal constellation, like Pisces, depicts the result of the sudden appearance of the earthborn giant Typhoeus. Bacchus was feasting on the banks of the Nile at the time, and jumped into the river. The part of him that was below water was transformed into a fish, while his upper body became that of a goat.
From this point of view, he saw that Typhoeus was attempting to tear Jupiter into pieces; he blew a shrill note on his pipes, and Typhoeus fled. Jupiter then placed the new shape of Bacchus in the heavens out of thanks for the rescue.
Capricornus has therefore from antiquity been represented by a figure with the head and body of a goat and the tail of a fish. It may be seen between Aquarius and Sagittarius low on the southern horizon.
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Cassiopeia, the Queen
Cassiopeia was the beautiful wife of Cepheus, king of Ethiopia, and the mother of Andromeda. She is most famous in connection with the myth of her daughter, Andromeda. The queen made the mistake of bragging she was more lovely than the Nereids, or even than Juno herself.
The goddesses were, needless to say, rather insulted, and went to Neptune, god of the sea, to complain. Neptune promptly sent a sea monster (possibly Cetus?) to ravage the coast. The king and queen were ordered to sacrifice their daughter to appease Neptune's wrath, and would have done so had Perseus not arrived to kill the monster in the nick of time. As a reward, the hero was wedded to the lovely Andromeda.
By most accounts, Cassiopeia was quite happy with the match. In some versions of the myth, however, the queen objects to the marriage and is turned to stone when Perseus shows her the head of the Gorgon Medusa.
Although she was placed in the heavens by Neptune, the sea-god saw fit to humiliate her one final time (and for all eternity). He placed her so that she is seated on her throne, with her head pointing towards the North Star Polaris. In this position, she spends half of every night upside-down.
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Cepheus, the King of Ethiopia
Cepheus, king of Ethiopia, was married to the beautiful Cassiopeia, and together they had a daughter, Andromeda. Although his name is most well-known in connection with his daughter, Cepheus was placed in the sky of his own right: He voyaged as an Argonaut with Jason on the quest for the Golden Fleece.
All three members of the family may be found in the northern sky; Cepheus and Cassiopeia are quite close to the northern celestial pole. Cepheus is generally represented as a robed king with a crown of stars, standing with his left foot planted over the pole and his scepter extended towards his queen.
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Cetus, the Whale
Cetus deserves mention because some say the constellation represents the sea monster sent to Ethiopia as punishment for the boasting of Queen Cassiopeia. The monster nearly kills Andromeda, daughter of Cassiopeia and Cepheus, but is itself killed by the hero Perseus.
More frequently, though, Cetus is represented as a whale, which implies no connection to the Andromeda myth. Either way, the constellation is appropriately a large one, and is relegated to the southern sky--far from Andromeda, Cepheus, Cassiopeia, and Perseus.
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Corona Borealis, the Northern Crown
This constellation is generally associated with Ariadne, the daughter of King Minos of Crete. His wife had borne a hideous monster, half-man and half-bull, and Minos had it shut up in a labyrinth designed by the famous architect Daedalus. The maze was so complex and confusing that Daedalus "was himself scarcely able to find his way back to the entrance" (Metamorphoses VIII 166-167).
Periodically, the Minotaur needed to be fed, and a number of Athenians would be put into the labyrinth for it to eat. This happened twice; on the third feeding, the hero Theseus was one of those chosen as a sacrifice. Ariadne fell in love with him, and offered to help if he would take her away with him when he escaped. He agreed, and she gave him a thread to unwind behind him to mark his passage. He killed the Minotaur, followed the thread out of the labyrinth, and sailed from Crete with Ariadne:
Immediately he set sail for Dia, carrying with him the daughter of Minos; but on the shore of that island he cruelly abandoned his companion. Ariadne, left all alone, was sadly lamenting her fate, when Bacchus put his arms around her, and brought her his aid. He took the crown from her forehead, and set it as a constellation in the sky, to bring her eternal glory.
Up through the thin air it soared and, as it flew, its jewels were changed into shining fires. They settled in position, still keeping the appearance of a crown, midway between the kneeling Hercules and Ophiucus, who grasps the snake. (Metamorphoses VIII 174-182).
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Cygnus, the Swan
As with so many of the constellations, there are a number of possible explanations for the presence of the swan in the heavens. Some myths, for instance, state the swan was once the pet of the Queen Cassiopeia. Other versions state that the swan was Cionus, son of Neptune, who was wrestled to the ground and smothered by Achilles. To save his son, Neptune immortalized Cionus as a swan.
Another story says the swan is Orpheus, who was murdered by the Thracian women while under the influence of Bacchus. Upon his death, the celebrated musician was placed in the heavens to spend eternity by his harp, Lyra. Yet another variant says that the swan represents the form taken by Jupiter when he deceived Leda and fathered Pollux.
According to Ovid, the swan was once Cygnus, son of Sthenele and a close friend of Phaethon. Phaethon died in the river Eridanus after attempting to drive the chariot of the sun, and Cygnus was overcome with grief that Jupiter could have struck down his friend:
As he mourned, his voice became thin and shrill, and white feathers hid his hair. His neck grew long, stretching out from his breast, his fingers reddened and a membrane joined them together. Wings clothed his sides, and a blunt beak fastened on his mouth. Cygnus became a new kind of bird: but he put no trust in the skies, or in Jupiter, for he remembered how that god had unjustly hurled his flaming bolt. Instead, Cygnus made for marshes and broad lakes, and in his hatred of flames chose to inhabit the rivers, which are the very antithesis of fire (Metamorphoses II 374-382).
Cygnus is easily found in the summer sky. Also called the Northern Cross because of its characteristic shape, its brightest star is Deneb, which is part of the Summer Triangle with Vega and Altair. Cygnus is located next to Cepheus and Lyra.
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Draco, the Dragon
It is unclear precisely which mythological dragon Draco represents. There are, however, three main contenders.
One version--the least likely--of the Draco story is that the dragon fought Minerva during the wars between the giants and the gods. Minerva threw Draco's twisted body into the heavens before it had time to unwind itself.
Another variant is that Draco represents the dragon who guarded the golden apples in the garden of the Hesperides. One of the labors of Hercules was to steal these apples (some sources state it was his eleventh labor, others it was his twelfth). This was, according to Bulfinch,
the most difficult labor of all..., for Hercules did not know where to find them. These were the apples which Juno had received at her wedding from the goddess of the Earth, and which she had entrusted to the keeping of the daughters of Hesperus, assisted by a watchful dragon. After various adventures, Hercules arrived at Mount Atlas in Africa. Atlas was one of the Titans who had warred against the gods, and after they were subdued, Atlas was condemned to bear on his shoulders the weight of the heavens. He was the father of the Hesperides, and Hercules thought might, if any one could, find the apples and bring them to him (Bulfinch's Mythology, 136).
Hercules suggested this plan to Atlas, who pointed out two problems: first, he could not simply drop his burden; second, there was the awful guardian dragon. Hercules responded by throwing his spear into the garden of the Hesperides and killing the hundred-headed beast, and then taking the burden on his own shoulders. Atlas retrieved the apples and, reluctantly taking the burden onto his shoulders once again, gave them to Hercules. Juno placed the dragon in the heavens as a reward for his faithful service.
By far the most commonly accepted version of Draco's arrival in the heavens, however, is that Draco was the dragon killed by Cadmus. Cadmus was the brother of Europa, who was carried off to Crete by Jupiter in the form of a bull (Taurus). Cadmus was ordered by his father to go in search of his sister, and told he could not return unless he brought Europa back with him. "Cadmus wandered over the whole world: for who can lay hands on what Jove has stolen away? Driven to avoid his native country and his father's wrath, he made a pilgrimage to Apollo's oracle, and begged him to say what land he should dwell in" (Metamorphoses III 9-11).
Cadmus followed Apollo's advice and found a suitable site for his new city. He sent his attendants to find fresh water to offer as a libation to Jupiter, and they wandered into a cave with springs. As they were getting water, however, they were all killed by "the serpent of Mars, a creature with a wonderful golden crest; fire flashed from its eyes, its body was all puffed up from poison, and from its mouth, set with a triple row of teeth, flickered a three-forked tongue" (Metamorphoses III 31-34). After his companions did not return, Cadmus himself went into the cave and discovered the dragon. He killed it with his spear, and then (upon the order of Minerva) sowed the dragon's teeth in the ground. From the teeth sprung warriors, who battled each other until only five were left. These five, along with Cadmus himself, were the first people of the city of Thebes.
It is interesting, however, to note that Ovid himself does not equate the dragon of Mars with Draco. In fact, in book III of Metamorphoses, he describes the dragon killed by Cadmus in terms of the constellation: "It was as huge as the Serpent that twines between the two Bears in the sky, if its full length were seen uncoiled" (45-47).
The Serpent described by Ovid is certainly the same one as we see today, twisting past Cepheus and between Ursa Major and Ursa Minor in the north, with its head beneath the foot of Hercules. Its location therefore seems to fit best with the myth that Draco was the dragon in the garden of the Hesperides.
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Eridanus, the River
Eridanus is a river in northern Italy, now known as the River Po. Called by Virgil the "king of rivers," Eridanus was made famous in connection with the death of Phaethon.
Phaethon was the son of Phoebus Apollo and the nymph Clymene. For his birthday one year, Phaethon asked his father for some proof that he was indeed the son of the sun-god. Apollo said he would give the boy any gift he desired as a token of his fatherly love, and Phaethon promptly asked for the chance to drive the chariot of the sun. His father balked, knowing that no mortal youth could possibly have the strength necessary to control the horses. However, Phaethon insisted, and Apollo had granted his word.
Phaethon drove off on the route of the sun, but sure enough, he could not control the powerful horses. He drove too close to the heavens, and then plunged too close to the earth, scorching both realms. Gaia endured the sun's heat until she could bear it no more, and then she called upon Jupiter for help:
The omnipotent father called upon the gods and even upon the sun himself, who had bestowed his car upon Phaethon, to be his witnesses that, if he did not bring help, the whole world would come to a grievous end. Then he mounted up to the highest point of heaven, that height from which he is wont to spread clouds over the broad lands of earth, whence he sends forth his thunderings and hurls his flashing bolts: he had no clouds then to draw over the world, no rain to shower down from the skies.
He sent forth a thunderclap and, poising his bolt close by his right ear, launched it against the charioteer....Phaethon, with flames searing his glowing locks, was flung headlong, and went hurtling down through the air, leaving a long trail behind: just as a star, though it does not really fall, could yet be thought to fall from a clear sky. Far from his native land, in a distant part of the world, the river Eridanus received him, and bathed his charred features" (Metamorphoses II 304-327).
As a constellation, Eridanus is the longest in the sky, meandering from Orion to Cetus.
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Gemini, the Twins
Gemini is a zodiacal constellation representing the twin brothers Castor and Pollux. Both were mothered by Leda, and were therefore brothers of Helen, but they had different fathers: In one night, Leda was made pregnant both by Jupiter in the form of a swan and by her husband, the king Tyndarus of Sparta. Pollux, as the son of a god, was immortal and was renowned for his strength, while his mortal brother Castor was famous for his skill with horses.
Both brothers voyaged in search of the Golden Fleece as Argonauts, and then fought in the Trojan War to bring their sister home to her husband Menelaus. They are traditionally depicted as armed with spears and riding a matched pair of snow-white horses.
The most common explanation for their presence in the heavens is that Pollux was overcome with sorrow when his mortal brother died, and begged Jupiter to allow him to share his immortality. Jupiter, acknowledging the heroism of both brothers, consented and reunited the pair in the heavens.
Castor and Pollux were unique among those placed in the sky in that they are not represented merely as a constellation but as actual stars which mark their heads in the constellation. Castor is bright white binary star, while Pollux is orange. They may be found between Cancer and Taurus.
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Hercules
Hercules was perhaps the greatest hero in all mythology. He was the son of Jupiter and Alcmena, and was hounded all his life by Juno. (This is deliciously ironic, because in the original Greek myths, Juno is named Hera and Hercules is Heracles, which means "glory of Hera.") Juno was unhappy with Jupiter's infidelity, and saw Hercules as a living, breathing symbol of her shame.
She delayed his birth, and when Hercules was a mere baby (but a big one!) sent two snakes into the crib he shared with his mortal half-twin Iphicles. Hercules killed them both with his bare hands, marking the beginning of his career as a monster-killer.
After a precocious childhood and adolesence, Hercules married Megara (daughter of Creon, king of Thebes). Juno succeeded in driving him mad, though, and he killed his wife and his children. As atonement, he serves the king Eurystheus, performing the twelve labors for which he is most famed:
He wrestled and killed the Nemean Lion (Leo) in its den, then used one of the beast's teeth to remove the otherwise impenetrable hide. He wore the hide as protection from then on.
He killed the Lernaean Hydra, a poisonous monster which could regenerate its heads, growing two each time one was lopped off. Hercules managed this by burning the stump of each before anything could grow back and burying the one immortal head beneath a rock. While battling the Hydra, his feet were nipped by a crab sent by Juno.
He captured the Cerynean Hind, a stag with golden horns which was famous for its speed, after a year-long pursuit.
He captured the Erymanthian Boar and killed the centaurs Pholus and Chiron who opposed him.
He successfully cleaned the Augean Stables, which had held 3000 oxen for thirty years without ever having been cleaned, in one night by redirecting the rivers Alpheus and Peneus through them.
He killed the Stymphalian Birds, which fed on human flesh in Arcadia.
He captured the Cretan Bull.
He captured the mares of Diomedes, which fed on human flesh, by feeding them their owner.
He stole the girdle of Hippolyta, queen of the Amazons.
He stole the man-eating cattle of Geryon.
He stole the three-headed guard dog Cerberus from the underworld.
He obtained the golden apples of the Hesperides, killing a dragon to do so.
Hercules also accompanied Jason on his quest for the Golden Fleece and assisted in the war between the gods and the giants. He remarried, and eventually died after accidentally poisoned by his wife Deineira. He was subsequently immortalized, even though he was by birth only half immortal.
The constellation Hercules, found between Lyra and Bootes, shows the hero wearing the skin of the Nemean Lion while holding his characteristic club and Cerberus the three-headed dog. He also rests his foot atop the head of Draco the dragon. The constellation is huge--the fifth-largest in the sky--but rather dim, which is an interesting parallel with Hercules himself. The hero was famed for his brawn, but his wits were rather lacking.
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Hydra, the Water-Snake
This constellation represents the Lernaean Hydra, slain by Hercules as his second labor. The Hydra was a multi-headed monster--according to Diodorus (first century B.C.), it had a hundred heads; Simonides (sixth century B.C.) said it had fifty.
The most common opinion, however, seems to be that it had nine. What made the Hydra so difficult was the fact that, whenever one of its heads was chopped off, two would grow in its place.
Hercules managed to get around this rather major obstacle by having his nephew, Iolaus, cauterize each stump with a hot iron as soon as Hercules could chop off a head. The hero then buried the monster's immortal head beneath a rock.
The task was made somewhat more difficult by Juno, who sent a crab to nip at the feet of Hercules while he battled the Hydra.
The Hydra is long and wandering, stretching almost from Canis Minor to Libra. It lies south of Cancer, Leo, and Virgo, and is best seen in the northern hemisphere during the months of February through May.
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Leo, the Lion
The zodiacal constellation Leo is generally accepted to represent the Nemean Lion, killed by Hercules during his first labor. According to myth, the Nemean lion had an impenetrable skin. Hercules got around this potentially serious obstacle by wrestling the lion and strangling it to death. He then removed one of its claws, and used it to skin the animal.
From then on, Hercules wore the skin of the Nemean Lion as protection.
Leo is easy to locate; following the pointer stars of the Big Dipper south approximates the location of the bright blue-white star Regulus in Leo's chest.
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Libra, the Scales
Libra is a zodiacal constellation. It represents the balance or scales, and is one of the oldest constellations. Although now associated with Virgo, a goddess of justice who had scales as the emblem of her office, it was once associated with the fall equinox. On that day, the days and nights are of equal length (i.e. the moon and the sun are in balance).
Libra is represented in the heavens next to the hand of Virgo.
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Lyra, the Lyre
Lyra is the lyre played by Orpheus, musician of the Argonauts and son of Apollo and the muse Calliope. Apollo gave his son the lyre as a gift, and Orpheus played it so well that even the wild beasts, the rocks, and the trees were charmed by his music. He fell deeply in love with the nymph Eurydice, and the two were married. Their wedded bliss did not last for very long, however. Eurydice was wandering in the fields with some other nymphs when she was seen by the shepherd Aristaeus. Aristaeus was struck by her beauty and pursued her; as she fled, she was bitten by a snake in the grass and died of the serpent's poison.
Orpheus was devastated. He decided to seek out his wife in the underworld, and gained an audience with Pluto and Persephone. The king and queen of the underworld, like all others, were charmed by his music and granted him permission to take Eurydice back to the land of the living with him:
They called Eurydice. She was among the ghosts who had but newly come, and walked slowly because of her injury. Thracian Orpheus received her, but on condition that he must not look back until he had emerged from the valleys of Avernus or else the gift he had been given would be taken from him.
Up the sloping path, through the mute silence they made their way, up the steep dark track, wrapped in impenetrable gloom, till they had almost reached the surface of the earth. Here, anxious in case his wife's strength be failing and eager to see her, the lover looked behind him, and straightaway Eurydice slipped back into the depths. Orpheus stretched out his arms, straining to clasp her and be clasped; but the hapless man touched nothing but yielding air. Eurydice, dying now a second time, uttered no complaint against her husband. What was there to complain of, that she had been loved? With a last farewell which scarcely reached his ears, she fell back again into the same place from which she had come (Metamorphoses X 47-63).
According to Ovid, Orpheus was so morose that he rejected the company of the Thracian women in favor of the company of small boys. The women were infuriated and, when maddened by the rites of Bacchus, hurled rocks at the bard. The rocks, tamed by the sound of the lyre, fell harmlessly at his feet until the screams of the infuriated women drowned out the music. The women dismembered Orpheus, throwing his lyre and his head into the river Hebrus. The Muses gathered up his limbs and buried them, and Orpheus went to the underworld to spend eternity with Eurydice. Jupiter himself cast the bard's lyre into the sky.
Lyra may be easily picked out in because it contains Vega, at zero magnitude the second brightest star in the northern sky. Vega is also part of the summer triangle, formed with Deneb and Altair.
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Ophiuchus, The Serpent Holder
The constellation Ophiuchus is the Serpent Bearer. This large constellation can be seen in the night sky from June through October. Although most of the stars are dim, Ophiuchus' teapot shape makes it easy to find. The constellation is a combination of three different figures.
Ophiuchus is holding Serpens Caput in his left hand, and Serpens Cauda in his right. He is located south of Hercules and north of Scorpius. In Greek myth, Ophiuchus represents the god of medicine, Asclepius. Asclepius was the son of Apollo and was taught by Chiron, the Centaur.
He learned how to bring people back from the dead, which worried Hades. The god of the underworld asked his brother Zeus to kill the medicine god. Zeus did strike him dead, but then put the figure of Asclepius in the sky to honor him. There aren't many bright stars in this constellation, but there is a rather unique one.
RS Ophiuchi is a type of star called a recurrent nova. These strange objects stay dim for long periods of time, and then suddenly brighten. Ophiuchus is full of celestial objects. There are numerous clusters and one nebula in the constellation.
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Orion, the Hunter
There are two different versions of the Orion myth, depending on the identity of his parents. The first of these identifies the sea-god Neptune as Orion's father and the the great huntress Queen Euryale of the Amazons as his mother. Orion inherited her talent, and became the greatest hunter in the world. Unfortunately for him, with his immense strength came an immense ego, and he boasted that he could best any animal on earth. In response to his vanity, a single small scorpion stung him and killed him.
Another version of the Orion myth states that he had no mother but was a gift to a pious peasant from Jupiter, Neptune, and Mercury. "Orion supposedly was able to walk on water and had greater strength and stature than any other mortal. A skilled blacksmith, he fabricated a subterranean palace for Vulcan. He also walled in the coasts of Sicily against the encroaching sea and built a temple to the gods there" (Magee, 48). Orion fell in love with Merope, daughter of Oenopion and princess of Chios. Her father the king, however, would not consent to give Orion his daughter's hand in marriage--even after the hunter rid their island of wild beasts. In anger,
Orion attempted to gain possession of the maiden by violence. Her father, incensed at this conduct, having made Orion drunk, deprived him of his sight and cast him out on the seashore. The blinded hero followed the sound of a Cyclops' hammer till he reached Lemnos, and came to the forge of Vulcan, who, taking pity on him, gave him Kedalion, one of his men, to be his guide to the abode of the sun. Placing Kedalion on his shoulders, Orion proceeded to the east, and there meeting the sun-god, was restored to sight by his beam.
After this he dwelt as a hunter with Diana, with whom he was a favourite, and it is even said she was about to marry him. Her brother [Apollo] was highly displeased and chid her [she was, after all, a virgin huntress], but to no purpose. One day, observing Orion wading through the ocean with his head just above the water, Apollo pointed it out to his sister and maintained that she could not hit that black thing on the sea. The archer-goddess discharged a shaft with fatal aim. The waves rolled the body of Orion to the land, and bewailing her fatal error with many tears, Diana placed him among the stars (Bulfinch's Mythology, 191-192).
It is also stated in some versions that Apollo, worried for Diana's chastity, sent a scorpion to kill Orion.
Orion is visible in the northern hemisphere in the south during the winter. He is generally shown as a hunter attacking a bull with an upraised club, and is easily recognizable by his bright belt of three stars. In addition, his shoulder is marked by the red supergiant Betelgeuse (literally "armpit of the central one" in Arabic), and his left leg is marked by the blue-white supergiant Rigel. According to the versions of the myth which have him killed by Scorpius, the two were placed on the opposite sides of the sky from each other so that they are never visible at the same time.
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Pegasus
Take a look at the story of how Perseus slew Medusa, the mother of Pegasus, and rescued Andromeda, the daughter of Cepheus and Cassiopeia, from the sea monster Cetus.
Pegasus was later brought to Mount Helicon by Bellerophon and with one kick of his hoof, he caused the spring of Hippocrene to flow. Hippocrene is said to be the source of inspiration to poets. Bellerophon, who slayed the hideous beast Chimaera, became so headstrong that he ordered Pegasus to fly him up to Mount Olympus, the home of the gods.
This impudence angered Zeus, who sent an insect to sting the winged horse, who bucked Bellerophon off its back. Needless to say, Bellerophon did not survive the fall to Earth. Pegasus went on to greatness, however, as the "Thundering Horse of Jove" who carried lightning bolts for Zeus.
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Perseus
Perseus was one of the great heroes of classical mythology. He was the son of Jupiter and Danae, and is best known for his killing of the Gorgon Medusa. This was a rather complex task, as anyone who saw her hideous face would be turned immediately to stone--the Gorgons, according to Bulfinch, were "monstrous females with huge teeth like those of swine, brazen claws, and snaky hair" (Bulfinch's Mythology, 109).
Perseus accomplishes it, however, by the aid of Pluto, Mercury and Minerva. Pluto lent his helmet of invisibility to Perseus, Mercury lent the hero his winged sandals, and Minerva allowed him the use of her shield. With the aid of the helmet and the sandals, Perseus was able to get within striking range without being detected by Medusa or the two immortal Gorgons. He then used the reflection on the shield to guide his killing blow, and flew off unharmed bearing the head of Medusa:
He was bringing back the Gorgon's head, the memorable trophy he had won in his contest with that snaky-haired monster. As the victorious hero hovered over Libya's desert sands, drops of blood fell from the head. The earth caught them as they fell, and changed them into snakes of different kinds. So it came about that that land is full of deadly serpents. Thereafter, Perseus was driven by warring winds all over the vast expanse of sky: like a raincloud, he was blown this way and that. He flew over the whole earth, looking down from the heights of heaven to the land which lay far below (Metamorphoses IV 615-624).
He was rather tired and wanted to rest when he arrived at the lands of Atlas, at the ends of the earth. Atlas, however, tried to turn him away with his considerably greater strength. Perseus was infuriated and showed him the head of Medusa, turning the Titan into "a mountain as huge as the giant he had been. His beard and hair were turned into trees, his hands and shoulders were mountain ridges, and what had been his head was now the mountain top. His bones became rock. Then, expanding in all directions, he increased to a tremendous size--such was the will of the gods--and the whole sky with its many stars rested upon him" (Metamorphoses IV 656-662). Perseus flew on until he spotted the beautiful maiden Andromeda, who was chained to the rocky shore as a sacrifice to a sea monster. Perseus promptly fell in love with her, killed the monster, and married the princess.
There are some variants on the myth of Perseus. According to some versions, he had to win the winged sandals and the helmet from the three Graeae, sisters of the Gorgons who shared one eye and one tooth among them. He stole the eye and the tooth, returning them only in exchange for the sandals and the helmet he needed to defeat Medusa.
When he died many years later, Perseus was immortalized as a constellation. He may be found near Andromeda and her parents, Cepheus and Cassiopeia, in the northern sky. The hero is depicted with a sword in one hand and the head of Medusa in the other; it is interesting to note the the eye of Medusa is the star Algol. Algol, which means "Demon Star" in Arabic, is an eclipsing binary star--it is normally about as bright as Polaris (second magnitude), but every two and a half days it becomes dimmer for roughly eight hours as the dimmer star of the pair passes between the brighter and the earth.
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Pisces, the Fish
The horrible earthborn giant Typhoeus suddenly appeared one day, startling all the gods into taking on different forms to flee. Jupiter, for instance, transformed himself into a ram; Mercury became an ibis; Apollo took on the shape of a crow; Diana hid herself as a cat; and Bacchus disguised himself as a goat. Venus and her son Cupid were bathing on the banks of the Euphrates River that day, and took on the shapes of a pair of fish to escape danger. Minerva later immortalized the event by placing the figures of two fish amongst the stars.
The zodiacal constellation Pisces represents two fish, tied together with a cord. The constellation is not particularly bright or easy to find, but is near Pegasus and Aquarius.
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Sagittarius, the Archer
The zodiacal constellation Sagittarius represents the centaur Chiron. Most of the centaurs were regarded in myth as bestial--they were, after all, half horse. However, the ancient Greeks had a great deal of respect for the horse, and so were reluctant to make the centaurs entirely bad. In fact, Chiron was renowned for his gentleness. He was an excellent archer, musician, and physician, and tutored the likes of Achilles, Jason, and Hercules.
Chiron, however, was accidentally shot and wounded by Hercules. The arrow, which had been dipped in the poison of the Lernaean Hydra, inflicted great suffering on Chiron--so great, in fact, that even the talented physician could not cure himself. In agony, but as an immortal unable to find release in death, Chiron instead offered himself as a substitute for Prometheus.
The gods had punished Prometheus for giving fire to man by chaining him to a rock. Each day an eagle would devour his liver, and each night it would grow back. Jupiter, however, had at the request of Hercules agreed to release Prometheus if a suitable substitute could be found. Chiron gave up his immortality and went to Tartarus in place of Prometheus; in recognition of his goodness, Jupiter placed him in the stars (Pasachoff, 139).
Sagittarius may be seen only in the summer from the northern hemisphere, and is visible low in the south. The Milky Way runs through Sagittarius.
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Scorpius, the Scorpion
Scorpius is a zodiacal constellation. The scorpion is generally believed to be responsible for the death of the great hunter Orion. According to some myths, the scorpion stung Orion in response to his boast that he could defeat any beast; according to others, it was sent by Apollo, who was concerned for his sister Diana's continued chastity.
In either case, Scorpius was placed in the opposite side of the sky from Orion so as to avoid any further conflict. It is to the southeast of Libra, and is marked by the bright red star Antares. (Antares is Greek for "Rival of Ares," the Greek war-god. The star is so named because of of its brightness and color, which are approximately the same as of the planet Mars.)
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Taurus, the Bull
Taurus is a zodiacal constellation. According to myth, Taurus represents the bull-form taken on by Jupiter when he became enamored of Europa, princess of Phoenicia:
Majesty and love go ill together, nor can they long share one abode. Abandoning the dignity of his sceptre, the father and ruler of the gods, whose hand wields the flaming three-forked bolt, whose nod shakes the universe, adopted the guise of a bull; and mingling with the other bullocks, joined in their lowing and ambled in the tender grass, a fair sight to see. His hide was white as untrodden snow, snow not yet melted by the rainy South wind.
The muscles stood out on his neck, and deep folds of skin hung along his flanks. His horns were small, it is true, but so beautifully made that you would swear they were the work of an artist, more polished and shining than any jewel. There was no menace in the set of his head or in his eyes; he looked completely placid.(Metamorphoses II 847-858).
The princess Europa was impressed by the beauty and gentleness of the bull, and the two played together on the beach. Eventually, Europa climbed onto the bull's back, and he swam out to sea with her. He took her to Crete and revealed his true self.
The constellation Taurus consists of only the head and shoulders of the snowy white bull. The representation in the stars seems to show a raging bull, however, always about to plunge into Orion, which is somewhat at odds with the story.
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Ursa Major, the Great Bear
Callisto was a maiden in the wild region Arcadia. She was a huntress, "not one who spent her time in spinning soft fibres of wool, or in arranging her hair in different styles. She was one of Diana's warriors, wearing her tunic pinned together with a brooch, her tresses carelessly caught back by a white ribbon, and carrying in her hand a light javelin or her bow" (Metamorphoses II 412-415).
Jupiter caught sight of her and immediately desired her. He took on the shape of the goddess Diana and spoke to Callisto, who was delighted to see who she thought was her mistress. She began to tell him of her hunting exploits, and he responded by raping her. "She resisted him as far as a woman could--had Juno seen her she would have been less cruel--but how could a girl overcome a man, and who could defeat Jupiter? He had his way, and returned to the upper air" (Metamorphoses II 434-437).
Callisto bore a son, Arcas, which infuriated Juno. Out of jealousy, the wife of Jupiter transformed the girl into a bear. She lived for a time in the wild, until Arcas came across her one day while hunting. He was about to kill the bear his mother, but Jupiter stayed his hand and transformed him into a bear as well. The king of gods then placed both mother and son into the heavens as neighboring constellations.
The constellation Ursa Major is quite commonly known. It includes the Big Dipper, perhaps the most-recognized feature of a constellation in the heavens.
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Ursa Minor, the Lesser Bear
Arcas was the son of Callisto, who was transformed by Juno into a bear. When Arcas was fifteen, he was out hunting in the forest when he came across a bear. The bear behaved quite strangely, looking him in the eyes. He of course could not recognize his mother in her strange shape, and was preparing to shoot her when Jupiter prevented him.
He too was transformed into a bear, and both mother and son were taken up into the sky. Juno was annoyed that the pair should be given such honor, and took her revenge by convincing Poseidon to forbid them from bathing in the sea. It is for this reason that Ursa Major and Ursa Minor are both circumpolar constellations, never dipping beneath the horizon when viewed from northern latitudes.
Ursa Minor is better known as the Little Dipper. Polaris, the star marking the end of the dipper's handle, is located at the north celestial pole.
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Virgo, the Virgin
Virgo is a zodiacal constellation. According to the ancient poets, the virgin is also sometimes known as Astraea. She lived on the earth during the Golden Age of man, which is described by Hesiod:
First a golden race of mortal men were
The "daimones" of which Hesiod speaks are invisible spirits which watch over men. Presumably, although it is unclear, Astraea is the daimone whose province is justice. The emblem of her office was therefore the scales (Libra), which are seen next to Virgo in the sky.
Virgo is the second largest constellation and is highest in the northern hemisphere during May and June. The brightest star in Virgo is Spica.
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These are the work of Cathy Bell (cmbell AT alumni princeton edu) for CLA 212.
RA: 1 hour
Dec: 40 degrees
Visible between latitudes 90 and -40 degrees
Best seen in November (at 9:00 PM)
ALPHERATZ (Alpha And)
MIRACH (Beta And)
ALMAAK (Gamma 1 And)
Adhil (Xi And)
M31 The Andromeda Galaxy (spiral galaxy)
M32 Satellite galaxy of Andromeda (elliptical galaxy)
M110 Satellite galaxy of Andromeda (elliptical galaxy)
RA: 23 hours
Dec: -15 degrees
Visible between latitudes 65 and -90 degrees
Best seen in October (at 9:00 PM)
SADALMELIK (Alpha Aqr)
Sadalsuud (Beta Aqr)
Sadalachbia (Gamma Aqr)
Skat (Delta Aqr)
Albali (Epsilon Aqr)
Ancha (Theta Aqr)
Situla (Kappa Aqr)
M2 (globular cluster)
M72 (globular cluster)
M73 (system or astrerism of 4 stars)
RA: 20 hours
Dec: 5 degrees
Visible between latitudes 85 and -75 degrees
Best seen in September (at 9:00 PM)
ALTAIR
(Alpha Aql)
ALSHAIN
(Beta Aql)
TARAZED
(Gamma Aql)
Deneb el
Okab (Epsilon Aql)
Deneb el
Okab (Zeta Aql)
RA: 3 hours
Dec: 20 degrees
Visible between latitudes 90 and -60 degrees
Best seen in December (at 9:00 PM)
HAMAL (Alpha Ari)
Sharatan (Beta Ari)
Mesarthim (Gamma 2 Ari)
Botein (Delta Ari)
RA: 15 hours
Dec: 30 degrees
Visible between latitudes 90 and -50 degrees
Best seen in June (at 9:00 PM)
ARCTURUS (Alpha Boo)
Nekkar (Beta Boo)
Seginus(Gamma Boo)
IZAR (Epsilon Boo)
Mufrid (Eta Boo)
Asellus Primus (Theta Boo)
Asellus Secondus (Iota Boo)
Asellus Tertius (Kappa 2 Boo)
Alkalurops (Mu 1 Boo)
Merga (38 Boo)
RA: 9 hours
Dec: 20 degrees
Visible between latitudes 90 and -60 degrees
Best seen in March (at 9:00 PM)
Acubens (Alpha Cnc)
Altarf (Beta Cnc)
Asellus Borealis (Gamma Cnc)
Asellus Australis (Delta Cnc)
Tegmen (Zeta 1 Cnc)
M44 Praesepe, The Beehive Cluster (open cluster)
M67 (open cluster)
RA: 21 hours
Dec: -20 degrees
Visible between latitudes 60 and -90 degrees
Best seen in September (at 9:00 PM)
Prima Giedi (Alpha 1 Cap)
Secunda Giedi (Alpha 2 Cap)
Dabih (Beta Cap)
Nashira (Gamma Cap)
Deneb Algedi (Delta Cap)
Alshat (Nu Cap)
M30 (globular cluster)
RA: 1 hour
Dec: 60 degrees
Visible between latitudes 90 and -20 degrees
Best seen in November (at 9:00 PM)
SHEDIR (Alpha Cas)
Caph (Beta Cas)
Ruchbah (Delta Cas)
Segin (Epsilon Cas)
Achird (Eta Cas)
Marfak (Theta Cas)
Marfak (Mu Cas)
M52 (open cluster)
M103 (open cluster)
RA: 22 hours
Dec: 70 degrees
Visible between latitudes 90 and -10 degrees
Best seen in October (at 9:00 PM)
ALDERAMIN (Alpha Cep)
Alfirk (Beta Cep)
Alrai (Gamma Cep)
Herschel's "Garnet Star" (Mu Cep)
Alkurhah (Xi Cep)
Al Kalb al Rai (Rho 2 Cep)
RA: 2 hours
Dec: -10 degrees
Visible between latitudes 70 and -90 degrees
Best seen in December (at 9:00 PM)
MENKAR (Alpha Cet)
DIPHDA (Beta Cet)
Kaffaljidhma (Gamma Cet)
Baten Kaitos (Zeta Cet)
Dheneb (Eta Cet)
Deneb Kaitos Shemali (Iota Cet)
Menkar (Lambda Cet)
MIRA (Omicron Cet)
Messier Objects
M77 (spiral galaxy)
RA: 16 hour
Dec: 30 degrees
Visible between latitudes 90 and -50 degrees
Best seen in July (at 9:00 PM)
ALPHEKKA (Alpha CrB)
Nusakan (Beta CrB)
RA: 21 hours
Dec: 40 degrees
Visible between latitudes 90 and -40 degrees
Best seen in September (at 9:00 PM)
DENEB (Alpha Cyg)
ALBIREO (Beta 1 Cyg)
Sadr (Gamma Cyg)
Gienah Cygni (Epsilon Cyg)
Azelfafage (Pi 1 Cyg)
Ruchba (Omega 2 Cyg)
M29 (open cluster)
M39 (open cluster)
RA: 17 hours
Dec: 65 degrees
Visible between latitudes 90 and -15 degrees
Best seen in July (at 9:00 PM)
THUBAN (Alpha Dra)
Rastaban(Beta Dra)
ETAMIN (Gamma Dra)
Nodus Secundus (Delta Dra)
Tyl (Epsilon Dra)
Aldhibah (Zeta Dra)
Ed Asich (Iota Dra)
Gianfar (Lambda Dra)
Arrakis (Mu Dra)
Kuma (Nu 2 Dra)
Grumium (Xi Dra)
Alsafi (Sigma Dra)
Dsiban (Psi 1 Dra)
Right Ascension: 3 hours
Declination: -20 degrees
Visible between latitudes 60 and -90 degrees
Best seen in December (at 9:00 PM)
ACHERNAR (Alpha Eri)
Cursa (Beta Eri)
Zaurak (Gamma Eri)
Rana (Delta Eri)
Zibal (Zeta Eri)
Azha (Eta Eri)
ACAMAR (Theta 1 Eri)
Beid (Omicron 1 Eri)
Keid (Omicron 2 Eri)
Angetenar (Tau 2 Eri)
Theemim (Upsilon 2 Eri)
Sceptrum (53 Eri)
RA: 7 hours
Dec: 20 degrees
Visible between latitudes 90 and -60 degrees
Best seen in February (at 9:00 PM)
CASTOR (Alpha Gem)
POLLUX (Beta Gem)
ALHENA (Gamma Gem)
Wasat (Delta Gem)
Mebsuta (Epsilon Gem)
Mekbuda (Zeta Gem)
Propus (Eta Gem)
Propus (Iota Gem)
Tejat Posterior (Mu Gem)
Alzirr (Xi Gem)
Propus (1 Gem)
M35 (open cluster)
RA: 17 hours
Dec: 30 degrees
Visible between latitudes 90 and -50 degrees
Best seen in July (at 9:00 PM)
RASALGETHI (Alpha 1 Her)
Kornephoros (Beta Her)
Sarin (Delta Her)
Marfik (Kappa Her)
Maasym (Lambda Her)
Kajam (Omega Her)
M13 The Great Hercules Globular Cluster (globular cluster)
M92 (globular cluster)
RA: 10 hours
Dec: -20 degrees
Visible between latitudes 60 and -90 degrees
Best seen in April (at 9:00 PM)
ALPHARD (Alpha Hya)
Al Minliar al Shuja (Sigma Hya)
M48 (open cluster)
M68 (globular cluster)
M83 (spiral galaxy)
RA: 11 hours
Dec: 15 degrees
Visible between latitudes 90 and -65 degrees
Best seen in April (at 9:00 PM)
REGULUS (Alpha Leo)
DENEBOLA (Beta Leo)
ALGIEBA (Gamma 1 Leo)
Zosma (Delta Leo)
Ras Elased Australis (Epsilon Leo)
Adhafera (Zeta Leo)
Chort (Theta Leo)
Al Minliar al Asad (Kappa Leo)
Alterf (Lambda Leo)
Ras Elased Borealis (Mu Leo)
Subra (Omicron Leo)
M65 (spiral galaxy)
M66 (spiral galaxy)
M95 (spiral galaxy)
M96 (spiral galaxy)
M105 (elliptical galaxy)
RA: 15 hours
Dec: -15 degrees
Visible between latitudes 65 and -90 degrees
Best seen in June (at 9:00 PM)
Zuben Elgenubi (Alpha 2 Lib)
Zuben Elschemali (Beta Lib)
Zuben Elakrab(Gamma Lib)
Zuben Elakribi (Delta Lib)
Brachium (Sigma Lib)
RA: 19 hours
Dec: 40 degrees
Visible between latitudes 90 and -40 degrees
Best seen in August (at 9:00 PM)
VEGA (Alpha Lyr)
Sheliak (Beta Lyr)
Sulafat (Gamma Lyr)
Double Double (Epsilon 1 Lyr)
Double Double (Epsilon 1 Lyr)
Double Double (Epsilon 2 Lyr)
Double Double (Epsilon 2 Lyr)
Aladfar (Eta Lyr)
Alathfar (Mu Lyr)
M56 (globular cluster)
M57 The Ring Nebula (planetary nebula)
RA: 17 hours
Dec: 0 degrees
Visible between latitudes 80 and -80 degrees
Best seen in July (at 9:00 PM)
RASALHAGUE
(Alpha Oph)
Cebalrai
(Beta Oph)
Yed
Prior (Delta Oph)
Yed
Posterior (Epsilon Oph)
Sabik
(Eta Oph)
Marfic
(Lambda Oph)
M9
(globular cluster)
M10
(globular cluster)
M12
(globular cluster)
M14
(globular cluster)
M19
(globular cluster)
M62
(globular cluster)
M107
(globular cluster)
RA: 5 hours
Dec: 5 degrees
Visible between latitudes 85 and -75 degrees
Best seen in January (at 9:00 PM)
BETELGEUSE (Alpha Ori)
RIGEL (Beta Ori)
BELLATRIX (Gamma Ori)
MINTAKA (Delta Ori)
ALNILAM (Epsilon Ori)
ALNITAK (Zeta Ori)
Nair al Saif (Iota Ori)
SAIPH (Kappa Ori)
Meissa (Lambda Ori)
Tabit (Pi 3 Ori)
Tabit (Pi 2 Ori)
Tabit (Pi 4 Ori)
Tabit (Pi 1 Ori)
Thabit (Upsilon Ori)
M42 The Great Orion Nebula (diffuse nebula)
M43 part of the Orion Nebula, de Mairan's Nebula (diffuse nebula)
M78 (diffuse nebula)
RA: 22 hours
Dec: 20 degrees
Visible between latitudes 90 and -60 degrees
Best seen in October (at 9:00 PM)
MARKAB
(Alpha Peg)
SCHEAT
(Beta Peg)
ALGENIB
(Gamma Peg)
ENIF
(Epsilon Peg)
Homam
(Zeta Peg)
Matar
(Eta Peg)
Baham
(Theta Peg)
Salm
(Tau Peg)
M15
(globular cluster)
RA: 3 hours
Dec: 45 degrees
Visible between latitudes 90 and -35 degrees
Best seen in December (at 9:00 PM)
MIRPHAK (Alpha Per)
ALGOL (Beta Per)
Miram (Eta Per)
Menkib (Xi Per)
Atik (Omicron Per)
Gorgonea Secunda (Pi Per)
Gorgonea Tertia (Rho Per)
Gorgonea Quarta (Omega Per)
M34 (open cluster)
M76 The Little Dumbell, Cork, or Butterfly (planetary nebula)
RA: 1 hour
Dec: 15 degrees
Visible between latitudes 90 and -65 degrees
Best seen in November (at 9:00 PM)
Alrisha (Alpha Psc)
Fum al Samakah (Beta Psc)
Torcularis Septentrionalis (Omicron Psc)
M74 (spiral galaxy)
RA: 19 hours
Dec: -25 degrees
Visible between latitudes 55 and -90 degrees
Best seen in August (at 9:00 PM)
Rukbat
(Alpha Sgr)
Arkab
Prior (Beta 1 Sgr)
Arkab
Posterior (Beta 2 Sgr)
Nash
(Gamma 2 Sgr)
Kaus
Meridionalis (Delta Sgr)
KAUS
AUSTRALIS (Epsilon Sgr)
Ascella
(Zeta Sgr)
Kaus
Borealis (Lambda Sgr)
Ain
al Rami (Nu 1 Sgr)
Albaldah
(Pi Sgr)
NUNKI
(Sigma Sgr)
Terebellum
(Omega Sgr)
Terebellum
(59 Sgr)
Terebellum
(60 Sgr)
Terebellum
(62 Sgr)
Messier Objects
M8
The Lagoon Nebula (diffuse nebula)
M17
The Omega, Swan, or Horseshoe Nebula (diffuse nebula)
M18
(open cluster)
M20
The Triffid Nebula (diffuse nebula)
M21
(open cluster)
M22
(globular cluster)
M23
(open cluster)
M24
Milky Way Patch (star cloud with open cluster)
M25
(open cluster)
M28
(globular cluster)
M54
(globular cluster)
M55
(globular cluster)
M69
(globular cluster)
M70
(globular cluster)
M75
(globular cluster)
RA: 17 hours
Dec: -40 degrees
Visible between latitudes 40 and -90 degrees
Best seen in July (at 9:00 PM)
ANTARES
(Alpha Sco)
Graffias
(Beta 1 Sco)
Dschubba
(Delta Sco)
Sargas
(Theta Sco)
SHAULA
(Lambda Sco)
Jabbah
(Nu Sco)
Grafias
(Xi Sco)
Alniyat
(Sigma Sco)
Alniyat
(Tau Sco)
Lesath
(Upsilon Sco)
M4
(globular cluster)
M6
The Butterfly Cluster (open cluster)
M7
Ptolemy's Cluster (open cluster)
M80
(globular cluster)
RA: 4 hours
Dec: 15 degrees
Visible between latitudes 90 and -65 degrees
Best seen in January (at 9:00 PM)
ALDEBARAN
(Alpha Tau)
ALNATH
(Beta Tau)
Hyadum
I (Gamma Tau)
Hyadum
II (Delta 1 Tau)
Ain
(Epsilon Tau)
ALCYONE
(Eta Tau)
Celaeno
(16 Tau)
Electra
(17 Tau)
Taygeta
(19 Tau)
Maia
(20 Tau)
Asterope
(21 Tau)
Sterope
II (22 Tau)
Merope
(23 Tau)
Atlas
(27 Tau)
Pleione
(28 Tau)
M1
The Crab Nebula (supernova
remnant)
M45
The Pleiades (The Seven Sisters), or Subaru (open cluster)
RA: 11 hours
Dec: 50 degrees
Visible between latitudes 90 and -30 degrees
Best seen in April (at 9:00 PM)
DUBHE
(Alpha UMa)
MERAK
(Beta UMa)
PHAD
(Gamma UMa)
MEGREZ
(Delta UMa)
ALIOTH
(Epsilon UMa)
MIZAR
(Zeta UMa)
ALKAID
(Eta UMa)
Talitha
(Iota UMa)
Tania
Borealis (Lambda UMa)
Tania
Australis (Mu UMa)
Alula
Borealis (Nu UMa)
Alula
Australis (Xi UMa)
Muscida
(Omicron UMa)
Muscida
(Pi 1 UMa)
Muscida
(Pi 2 UMa)
ALCOR
(80 UMa)
M40
Winecke 4 (double star)
M81
Bode's Galaxy or Bode's Nebula (spiral galaxy)
M82
The Cigar Galaxy (irregular galaxy)
M97
The Owl Nebula (planetary nebula)
M101
The Pinwheel Galaxy (spiral galaxy)
M108
(spiral galaxy)
M109
(spiral galaxy)
RA: 15 hours
Dec: 70 degrees
Visible between latitudes 90 and -10 degrees
Best seen in June (at 9:00 PM)
POLARIS (Alpha UMi)
KOCAB (Beta UMi)
Pherkad (Gamma UMi)
Yildun (Delta UMi)
Pherkad Minor (11 UMi)
made by the immortals who have Olympian homes.
They lived in Kronos' [Saturn's] time, when he ruled the sky,
they lived like gods, with carefree heart,
free and apart from trouble and pain; grim old age
did not afflict them, but with arms and legs always
strong they played in delight, apart from all evils;
They died as if subdued by sleep; and all good things were theirs;
the fertile earth produced fruit by itself,
abundantly and unforced;
willingly and effortlessly they ruled their lands with many goods.
But since the earth hid this race below,
they are daimones by the plans of great Zeus [Jupiter],
benevolent earthly guardians of mortal men,
who watch over judgments and cruel deeds, clothed in air and roaming over all the earth (Works and Days 109-125).
RA: 13 hours
Dec: 0 degrees
Visible between latitudes 80 and -80 degrees
Best seen in May (at 9:00 PM)
SPICA
(Alpha Vir)
Zavijah
(Beta Vir)
Porrima
(Gamma Vir)
Auva
(Delta Vir)
VINDEMIATRIX
(Epsilon Vir)
Heze
(Zeta Vir)
Zaniah
(Eta Vir)
Syrma
(Iota Vir)
Rijl al
Awwa (Mu Vir)
M49
(elliptical galaxy)
M58
(spiral galaxy)
M59
(elliptical galaxy)
M60
(elliptical galaxy)
M61
(spiral galaxy)
M84
(elliptical galaxy)
M86
(elliptical galaxy)
M87
Virgo A (elliptical galaxy)
M89
(elliptical galaxy)
M90
(spiral galaxy)
M104
The Sombrero Galaxy (spiral galaxy)
Close
Amateur Astronomy 101
RL = 2.456*R*(p'/p)^(1/3)
where p' is the density of the planet, p is the density of the moon, and R is the radius of the planet. (more)
Amateur astronomers occasionally seek advice on telescope buying, learning the sky, observing skills, and so on. Here are some thoughts.
What to do First.
Written words do not replace experience. Join an astronomy club, go to observing sessions, try others' telescopes. You will learn a lot.
To find clubs, ask at science stores, museums, and planetariums. College physics or astronomy departments may know, though clubs aren't their line. The magazines Sky & Telescope and Astronomy publish annual directories of clubs, stores, observatories, and such. Find them on newsstands, or in a library -- or try their respective web pages,
http://www.skypub.com
http://www.kalmbach.com/astro/astronomy.html
Been to a club already? Honest? Okay, keep reading...
If you have a telescope, you might skip on to "What about observing skills?" Otherwise, here are some hints on telescope selection.
Hey! Just Tell Me What To Buy.
If you must be led by the nose, I have put specific recommendations in a postscript at the end. Just don't come crying when you find you would have made a better decision with more homework: I told you so!
Some Basic Questions.
In buying a telescope, you face bewildering, expensive choices. To deal with the confusion, ask yourself these questions.
How much effort will you put into learning the sky? If you know the constellations, and have practiced finding things by "star-hopping" -- with charts instead of dial-in or punch-in coordinates -- you will be able to use a telescope cheaper, smaller, lighter, and easier to set up than one using precise alignment or computer control to locate objects.
How much effort will you spend on your observing skills? Seeing fine detail in celestial objects, or just seeing faint ones at all, takes practice and special knowledge. Yet the rewards are great: An experienced observer may see things with a small telescope that a beginner will miss with one five times larger, even with objects and sky conditions that favor both telescopes equally.
How far must you lug your telescope to get to where you use it, by what means, and how much effort will you put up with? Differences in size and design make differences in portability: Any telescope you take out and use is better than one so heavy or cumbersome that it stays in the closet.
Are you into fancy technology for its own sake, even if not useful or cost effective? If so, fine -- me, too. But if not, take care technology fans don't sell you things you don't need.
Do you want to take photos or CCD images of celestial objects? That's expensive. Folks who do it -- I don't -- often take several telescopes and several years to be satisfied, and spend lots of money.
With these thoughts in mind, I can make some general comments.
Some Realities.
The most important determinant of telescope optical performance is the diameter of the beam of light it accepts -- its "clear aperture". More light shows fainter things, and less obviously, clear aperture limits image detail, via physical optics. Bigger telescopes produce sharper images, just because they are bigger. Clear aperture is so important that telescopes are usually labeled by it -- a six-inch instrument takes in a six-inch diameter beam of light, and so on.
There are some qualifiers.
First, bad craftsmanship can make any telescope perform poorly. Yet it is not hard to make small telescope optics: Most companies usually turn out decent units, and if not, many manufacturers will often fix or replace a lemon, if you have wit to recognize one, and will to complain. (Many have neither; that's how some manufacturers make money!)
Second, different designs perform differently. Schmidt-Cassegrains, Newtonian reflectors, and refractors all have good and bad points. Folks who love telescopes, or sell them, will be eager to debate their merits, but variations in optical performance among telescopes of the same aperture and quality of optical work are relatively minor. They usually correspond to aperture changes of only 10 or 20 percent. Shabby optical work will increase that percentage enormously. One special case: For delicate planetary detail, a fine refractor may do 50 percent better than a fine example of any other common design.
Third, atmospheric turbulence ("seeing") keeps a telescope from showing detail, and sky brightness keeps it from showing faint objects. Poor seeing hits large telescopes harder than small ones. In poor seeing, there may be no reason to set up a big telescope, so if you always observe in such conditions, you may not want to buy one. Yet even in bright sky, a large telescope will show fainter stuff than a small one, and many of us have found dark-sky, stable-seeing sites not too far from home: From sites an hour from San Francisco Bay, sometimes I have to stare through the eyepiece of my Celestron 14 for several minutes before I can tell there is any air between me and what I am looking at.
Notwithstanding these caveats, APERTURE WINS, and wins big. If you buy the finest 90 mm fluorite refractor in the world, be braced for a junior high school student to make a 6-inch Newtonian that blows it out of the water. The 6-inch I made at 13 puts my world-class 90 mm fluorite to shame, and not because I was a master optician at 13, but because six inches is bigger than 90 mm, hence intrinsically better.
Hundreds of deep-sky objects show well with two-inch aperture at low magnification: Medium sized binoculars -- 7x50 or 10x50, say ("7x50" means "magnifies 7 times, 50-mm aperture") make simple, highly portable, inexpensive beginner instruments. Do you have one? To use them well, learn the sky enough to find things with a hand-held instrument. Don't get one that gets too heavy to hold steady before you are done observing.
Speaking broadly:
The most optical performance per unit of clear aperture comes from modern, high-quality refractors -- which are outrageously expensive compared to other designs of the same aperture. Also, in sizes much above four-inch aperture, the tubes are usually long enough to make the whole instrument cumbersome and heavy.
The most optical performance per unit of portability comes from Schmidt-Cassegrain and Maksutov designs -- but they are still pretty expensive.
One qualifier: Their portability comes from short tubes, but for small apertures -- four inches or less -- portability of all types is dominated by clumsiness of the tripod, so the advantage of Schmidt- Cassegrains and Maksutovs diminishes.
The most optical performance per unit of cost comes from Newtonians -- particularly those with Dobson mountings. They are clumsier than Schmidt-Cassegrains and Maksutovs of the same aperture, but not nearly as clumsy as refractors.
Let me regroup that information into three common questions:
What gives most optical performance for a given aperture?
Usually, a high-quality refractor.
What gives most optical performance for a given car to carry it?
Usually, a Schmidt-Cassegrain.
What gives most optical performance for a given budget?
Usually, a medium to large Dobson.
Though costly and cumbersome, small refractors are durable and hard to get out of whack. Good ones make decent beginner instruments, particularly for beginners with extra thumbs. A good small refractor makes it easy for an experienced observer to embarrass folks with giant Newtonians, who lack observing skills to exploit them. But BEWARE of mass-market junk refractors, advertised as high-power and sold in department stores.
Alt-azimuth mountings tend to be cheaper, lighter, less clumsy, and more quickly set up than equatorial ones, but to use one you must learn the sky enough to find things without dialing in coordinates. (Computer controls allow use of celestial coordinates to find things, and may look them up in a database for you, but they are not cheap.)
There's another way to look at this material. There are ecological niches for telescopes, corresponding to different uses and requirements. I know of seven:
Big Iron: This is the giant Dobson-mounted Newtonian, or humungeous Schmidt-Cassegrain, that fills your garage. To transport it requires a small trailer, pickup truck, or panel van, and setting it up calls for the concerted efforts of three used fullbacks and a circus elephant. The ladder to climb to the eyepiece is so tall you need supplemental oxygen to deter altitude sickness. This telescope is your galaxy-gazer and cluster-buster supreme, and if well made, then when the seeing is good it will show detail those condescending high-tech dweebs with their confounded itty-bitty apochromatic refractors can only dream about.
My "Big Iron" is a Celestron 14, with a little tiny single-axle cargo trailer to haul it.
Largest Conveniently Portable Telescope: This is the most telescope that will fit in your regular vehicle without hiring a bulldozer to clean it out. What it is, depends on your vehicle -- with a ten-speed, or a subway train, you have a problem. An eight- to eleven-inch Schmidt-Cassegrain is just right for many; that is one reason these telescopes are popular.
I have had several Largest Conveniently Portable Telescopes, over the last few cars. Once I built an eight-inch Dobson designed so the tube just barely fit across my back seat. I used it a lot till I bought a smaller car. For a while, my Largest Conveniently Portable Telescope was a Vixen 90 mm f/9 fluorite refractor on an altazimuth fork or a Great Polaris German equatorial (I have both), but now I use a six-inch f/10 Intes Maksutov on the Great Polaris. A faster Dobson than my 8-inch would do, with more performance for most purposes.
Public Star Party 'Scope:? This is something portable, with the added provisos that it's nice to have a drive, so you won't have to re-point between viewers, and that it should not be so expensive you worry about kids and idiots. An SCT will do.
I put the Intes or the Vixen fluorite on the Great Polaris, but I set the tripod legs to maximum length, so the expensive optics are out of reach. So far, no one has slam-dunked a rock.
Quick Look 'Scope: The idea is to leave something set up in the entrance hall, or hidden under a stack of Sky & Tel s in the car, all ready on a minute's notice if a truly close comet comes whizzing by, or if you are too lazy to assemble one of your real telescopes. Such an instrument can also double at nature watching or spying on the neighbors, which may be the same thing -- but don't tell your fellow astronomers, or you will lose observer points. Many of us have a spotting 'scope on a light tripod, or a 90 mm Maksutov on a heavy one.
I have a couple of small refractors that do yeoman duty as Quick Look 'Scopes. I am particularly fond of a 63 mm f/5.6 Brandon on a light photographer's tripod.
Binocular: A binocular can do much of what a Quick Look 'Scope does. I have too many: For astronomy I use a 7x35 Tasco (from Sears, $29.95) that I keep in my car for birding (oops, lost observer points), a Swift Commodore Mark II 7x50 (out of production), which was one of the first binoculars I saw with BAK-4 prisms, and an Orion 10x50 and 10x70 with BAK-4 prisms and multicoated everything, up to but not including the case. At star parties I wander around with a binocular dangling from my neck. I tried two, but ran out of eyes.
High-Tech Conversation-Stopper: This is how you shame those grass-chewing hillbilly clodstompers whose giant cardboard Dobsons have tubes so big they echo. Odds are the seeing will never get good enough to demonstrate that a half meter shaving mirror will blow eighteen centimeters of optical perfection clean out of the water, and when they go on about faint galaxies, you can change the subject to diffraction rings and modulation transfer functions, and ask them to compare internal baffles and background sky brightness. Besides, your telescope has more knobs than all theirs put together, and it cost more than all theirs put together, too.
The default choice for the High-Tech Conversation-Stopper these days is typically an apochromatic refractor, or something close ("apochromat" is a precise technical term; not all superb refractors are apochromats, and vice-versa), which if well made and well baffled will deliver outstanding performance for its size. Available sizes suffice for many amateurs who have recovered from aperture fever or not yet succumbed, or who have exhausted their supply of fullbacks and circus elephants to set up the Big Iron. Few other telescopes types qualify -- you're not allowed to have a Schiefspiegler unless you can spell it, and nobody wants a Yolo because people expect you to walk the doggie. Some folks like Questars, but not me.
My High-Tech Conversation-Stopper is the 90 mm Vixen fluorite I mentioned earlier. It is too small to be really impressive, and is short on knobs, but I talk fast enough to make up the difference.
CyberScope (Suggested by Bill Arnett): With the processor power of a microwave oven and servomechanisms accurate enough to bring an object into the field of a medium-power eyepiece, a computer- controlled telescope declares to astronomers and computer types alike the owner's level of sophistication in both disciplines. Advanced versions log observations in your own digitally simulated handwriting, brew coffee to keep themselves awake, and buy off local raccoons with Oreos, all while you sit inside at your real computer, writing space- combat video games in graphically-enhanced modularized compiled Tiny BASIC for Windows 95 NT. The battery truck is huge.
CyberScopes do a decent job of locating large numbers of objects from an internal database, and permit motorized tracking with a telescope lighter, less bulky, simpler to set up and align, and lots more expensive than if it were equatorially mounted. Low-quality mechanisms and sloppy construction often restrict their potential. Even so, those fond of technology may like them a lot, and folks with skill and equipment to program the control interface have a field day doing things most of us have never dreamed of.
I do not presently own a CyberScope. That's because I write programs for a living, and too many of them. In my hobbies, I avoid anything suspected to contain electrons.
What about accessories?
I have already said most of what you need to know about accessories, which is that (A) aperture wins. If you are budgeting a telescope, and eyepieces, finders, and such account for most of your funds, think more on what you plan to do -- it might be better to get a bigger telescope instead of fancy accessories. A 10-inch telescope with a hand magnifier as eyepiece will give a better view of most objects than an 8-inch with the world's best eyepieces. Why? Because (A) aperture wins.
Yet if you are up against limits of telescope portability, or have lots of money, or like technology, go ahead and buy fancy accessories. I won't tell, provided you remember that (A) aperture wins.
In any case, I will mention some plain-vanilla accessories that you might want to have, and maybe a few chocolate ones, too:
Eyepieces: A few good ones are better than many bad ones. You need a low-power, wide-field eyepiece, to find things and to see big, faint, diffuse objects. It might have magnification equal to one fifth the telescope clear aperture, in millimeters. On my f/11 Celestron 14, the low-power eyepiece has a 55 mm focal length, and is mounted in a two- inch barrel, so the front lens -- which sets field diameter -- can be as large as possible. (In smaller telescopes, internal baffles may mean no light gets to the edge of a two-inch wide eyepiece; if so, don't bother paying for one.) On my f/5 8-inch Dobson, I use a 20 mm Erfle eyepiece, which doesn't need a two-inch barrel.
The next power you will likely reach for is medium to medium high, to see details. Such an eyepiece might give magnification roughly equal to telescope clear aperture, in millimeters. On my C-14 I use a 12.4 mm eyepiece, and on my 8-inch Dobson, a 4 mm. The objects you look at with this power probably won't be very wide, so for economy, you might not want a super-wide-field type.
Your next choices will depend on what you like to look at. If you are not sure, hold off buying more eyepieces till you find out.
"Fast" f-numbers, typical in Dobson-mounted Newtonians, need fancy, expensive eyepieces to give good views, because the steeply converging light cones of these instruments are difficult for an eyepiece to cope with, particularly away from the center of the field. Slow instruments can use simpler eyepiece designs. A "Catch-22" of amateur astronomy is that cheap telescopes (fast Dobsons) need expensive eyepieces, but expensive telescopes (most refractors and Schmidt-Cassegrains, with slow f numbers) can use cheap eyepieces.
"Zoom" eyepieces change focal length at the twist of a knurled ring, but tend not to be very good. Barlow lenses, also called telextenders, multiply the focal length of a telescope: It used to be that they generally worked well only with telescopes with large f-numbers, where they were not needed -- another "Catch-22". There are now Barlow lenses that work with fast telescopes, where they are needed, but I urge a try-before-you-buy approach to selecting one.
For over fifteen years I used an eyepiece set bought in 1980. It had no fancy designs, just a 55 mm Plossl, 32, 20, and 12.4 mm Erfles, and 7 and 4 mm Orthoscopics. The 55 and 32 mm eyepieces were in 2-inch barrels, the others in 1.25 inch barrels. All were good quality -- the 55 and 32 mm were from University Optics, and the others were Meade Research-Grade. All worked reasonably, even at f/5, and the 68-degree apparent field of the Erfles was enough so I was not tempted by wider-field types. Besides, a big Erfle is already so heavy that I must rebalance the telescope to use one. I did use the 4 mm eyepiece on the C-14, but only rarely.
In mid 1996 I bought some more. I found that decent Plossls are comparable to Orthoscopics. I got some Vixen "Lanthanum" eyepieces, with built-in Barlow lenses to give 20 mm eye relief, even at such short focal lengths as 2.5 mm. Even without glasses, long eye relief makes viewing more relaxed: I don't worry about bumping the eyepiece. It also helps with public viewing: I focus with glasses on, and tell folks to leave theirs on and not refocus.
Note what high-tech eyepieces can and cannot do. The best give wider fields, with fewer eyepiece aberrations near the edges, than older types. The improvement is most noticeable at fast f numbers. If that matters to you, you might want some. But eyepieces are not aperture stretchers. They cannot increase image detail beyond the theoretical limit for the aperture, or increase the number of photons that make it to your eye. If you think otherwise, you are making the same mistake as the clueless beginner who buys a drug-store refractor because the box shouts "Magnifies 675 Times!!!". The best an eyepiece can do is not make things worse. A simple eyepiece, with good coatings and well-polished lenses, will show all the on-axis detail a telescope has, and absorb and scatter almost no light. That's what counts most for astronomical work.
In 1980, I bought several Ramsden eyepieces -- an old, simple, design -- for some ten dollars each. I use them at star parties without telling. They have only four air/glass surfaces, so simple coatings give good throughput, and there are few chances for bad polish to scatter light and ruin contrast. The field of view is narrow, but on axis, at slow f numbers, they give up nothing to new designs; images are superb.
Finders: What kind of finder you get depends on how you use it. If you look mostly at fine details in bright objects, you might buy a big finder, so what you look at will be visible in it, too. But if you push your telescope to its faint-object limits, you would need a finder as big as the main telescope. You might then consider one that shows stars exactly as faint as on your charts. It helps a lot in identifying stuff in the finder, if every star you see is charted, and vice-versa. Once the right pattern of stars is in the finder, you can put the crosshair where the object lies, even if it is too faint to see.
In dark sky, the 10x40 finder on my C-14 shows stars to magnitude 9.5, which matches my big charts. The 7x35 on my 6-inch Maksutov does almost as well. In suburbia, the 5x24 finder on my 8-inch Dobson goes to about magnitude 6.5 (which would be the naked-eye limit in darker conditions), thus matches many naked-eye star atlases.
Unit-power finders, like the Telrad, let you view the sky with both eyes, and see a pattern of light where your telescope is pointing. A cardboard and tape peep sight may work as well, and will be much cheaper, and any magnifying finder in which you face where the finder is pointing, can be used with both eyes open -- just let your brain fuse the images from both eyes. I tried a unit-power finder (Orion's) on my 90 mm refractor, but found it inferior to the original 6x30 finder. My opinion on unit-power finders is in the minority. Some folks use the Telrad's circles of known diameter to measure distances when finding things. I suggest you practice with both, then decide which is for you.
Charts: Preferences vary greatly. What I find useful, in order from simple to complicated, is more or less the following:
A simple planisphere, preferably a plastic one that won't sog out with dew and that may survive being sat upon. It's a fast way to find out whether a particular object is up before I go observing, or to check how long before it is well-placed.
A "pocket atlas". I am particularly fond of Ridpath and Tirion's The Night Sky , from Running Press in Philadelphia, PA. It is about three by five inches and half an inch thick, and out of print. Write Running Press and complain.
A "table atlas", bound as a book that will lie reasonably flat, with stars to the naked-eye limit, and many deep-sky objects to boot. I happen to use an old Norton's Star Atlas ; there are others.
A "deep atlas", like Uranometria 2000 , the AAVSO atlas or the new Millennium Star Atlas , with stellar magnitude limit of 9 or more and a vast number of objects. What's important here is to have plenty of charted stars in every finder field.
A planetarium computer program (Bill Arnett reminded me). If you are a beginning astronomer, I do *not* suggest you rush out and buy a computer, but if you already own one, you might bear in mind that there are programs that will turn your console into a window onto the simulated heavens, with features for finding, displaying, and identifying things. I happen to have the rather old Voyager 1.2 for my even older Macintosh II; there are plenty more, both for Macs and for the world descended from MS-DOS.
Some folks run such a program on a laptop, at the telescope. Please put red cellophane over the screen, if you do.
I have little use for the popular oversize-format charts with lesser magnitude limits, like 7.5 to 8.5; they don't show enough stars to be useful with my finders, and are too cumbersome. The plastic-laminated versions make good place mats, though. Everyone should use the box of a Dobson as a picnic table at least once.
A red flashlight: so you can read your charts and notes without ruining your night vision. Kinds with a glowing red diode instead of a bulb are particularly good. If other observers scream and throw things, your light is probably too bright.
A logbook This item is not for everyone. I like to record my observations, even if I merely note that I saw a certain object with a certain telescope and magnification. Logbooks make fun reading when it is cold or cloudy, and often there is reason to look up something later. Besides, if you quote often from your logbook, you can make people think you are an active observer when you gave it up years ago.
What about observing skills?
Even some experienced amateur astronomers think that seeing things comes free and easy, with no more effort than opening your eyes: But as current popular slang so evocatively articulates,
** NOT **.
Vision is an acquired skill. You must learn it, you must practice, and you must keep learning new things, and practicing them, too. Buying a big telescope to see better is like buying a big pot to cook better, or a big computer to program better. It might help, but cooking and programming depend more on knowledge and experience than on hardware. So does visual astronomy. People with garages full of telescopes (I can't close the door to mine) are victims of materialism, marketeering, and hyperbole. Practice is cheaper, and works better. As I said before, an experienced observer may see things with a small telescope that a beginner will miss with one five times larger.
What skills may you hope to cultivate? What techniques should you practice? Not all have names, but here are a few, in what I think is order of importance; what matters most comes first.
Patience: It can take a long time to see everything in a field, even if you know exactly what you are looking for.
Persistence: Eyes, telescope, and sky vary from night to night.
Dark adaptation: Avoid bright lights before observing: It takes your eyes hours to reach their full power of seeing faint objects.
Averted vision The part of your retina that sees detail best, sees low light worst. Look "off to the side" to find lumps in the dark. Many observers use averted vision on faint objects, but forget it for bright ones. Detecting something doesn't mean you've seen all of it. Don't let the dazzle of a galaxy's lens make you miss spiral arms that go beyond the field edge. How about increasing magnification, and using averted vision to seek more detail in the paler, larger, image? Averted vision helps with double stars, when one star is much fainter than the other, even if the faint star is bright enough not to need averted vision if it were by itself. I don't know why.
Stray light avoidance: Even when it's dark, background glow interferes with detecting faint objects. Keep it out of your telescope and out of your eyes. Try eye patches, and eye cups for eyepieces. My first view of the Sculptor Dwarf Galaxy was with my jacket collar pulled up over my binocular eyepieces. I looked like a cross between the Headless Horseman and the Guns of Navaronne, but I saw the galaxy.
Changing magnification: Old sources about observing faint objects sometimes suggest only such low magnifications as 0.15 to 0.20 times the telescope aperture in millimeters. Yet I sometimes find best detection of faint galaxies at magnifications of 1.0 times telescope aperture in millimeters. For bright objects in poor seeing, many people back off the magnification till seeing jitter is not visible, but doing so foregoes glimpses of fine detail when things are momentarily steady. If you don't change magnifications, you can't be sure you are using the best one.
Focusing critically: Particularly at higher magnification, precise focus is important to see all the detail. In poor seeing, it can take a long time to get the focus set right, but it's worth doing.
Moving the telescope: The eye sometimes detects motion, or changing levels of brightness, more easily than static images. Jiggle the telescope, or move it back and forth, to make an object "pop out", perhaps only in the moment just after the motion stops. Try all this while using averted vision.
Not moving the telescope: The eye sometimes adds up photons over many seconds; if you can hold your eye still for a long time, faint things may appear. Try it with averted vision.
Respiratory and circulatory health If you smoke, try taking a break before and during observing -- carbon monoxide from incomplete combustion interferes with the ability of the blood to transport oxygen.
Specific Recommendations For The Lazy.
If you are too lazy to do your homework, for shame! Oh, all right, here are some recommendations, but since you forfeit any claim to making an informed decision, I will not explain or justify them.
1) If you have a binocular, take it out and use it.
2) If you have no binocular, get one. Buy a Tasco model 2001, which has 35 mm diameter front lenses and magnifies seven times. It sold in Sears for $29.95 (US), last time I looked. It is second rate, but good value. Try it in the store: Make sure it doesn't rattle, and that you can get usable images from it. Do not buy the similar "zoom" unit.
3) For a star atlas and observing guide, buy Norton's 2000.0 Star Atlas and Reference Handbook , 18th edition, edited by Ian Ridpath. Sky Publishing Corporation lists it in their 1997 catalog at $49.95 (US). They have a web address, http://www.skypub.com, and an 800 number, 1-800-253-0245.
If you simply must have a telescope right away...
4) Do not buy a refractor. Not having done homework means you cannot tell wheat from chaff: Junk refractors abound.
5) Buy a Meade DS-2114ATS from the eBay Meade Factory Outlet. They are all refurbished, and just as good as the ones you would buy in the store for a much larger price. The DS-2114 isn't the greatest scope in the world, but it allows you to see a lot of things a newbie would not not see otherwise. For the price it isn't too bad. Later I suggest upgrading to a larger Dob. - ElWampa
I say again, you will make a better decision and be happier with your purchases, if you join a club and do some homework first. I repeat: You will make a better decision and be happier with your purchases, if you join a club and do some homework first. Good luck!
By, Jay Reynolds Freeman – freeman@netcom.com -- I speak only for myself.
If you have purchased a telescope, the next thing you're going to want is another eyepiece. (And after that, some filters, and after that...) I recommend getting the best eyepieces that you can afford and to be patient. There are good deals out there, but like anything else, you have to know what you want BEFORE you buy!
When I was starting out, I was completely lost when presented with all of the choices in eyepieces. With that in mind, the purpose of this article is to educate beginners on the merits of many of the types from a Huygens to a Nagler.
Eyepieces come in several diameters: 0.96 inches, 1.25 inches, and 2 inches. The 0.96 inch eyepieces are generally found on cheap department store telescopes, I would not recommend buying a telescope only capable of using them, as they can be very difficult to find.
The more common sizes are 1.25" and 2.0".
Eyepieces not only vary in size, and focal length but also in design. The simple designs give acceptable performance and in some cases even excellent performance. An extensive list of eyepieces and their specifications, type and cost may be found in the Advanced section of this website, under the "Technical Data" area. See Eyepiece Specifications.
The cost of an eyepiece is generally determined by its complexity. The market is literally flooded with eyepieces, all of which are geared to achieving the best field of view, magnification without sacrificing image quality.
Galileo, Kepler and Newton didn't have too many choices when they were picking out their eyepieces. The eyepiece that Galileo used was a single concave lens. The images it produced were very small and full of aberrations. Kepler improved the design a bit when he developed a convex lens that produced a wider field of view, but the image was inverted and still had a lot of aberrations. The progress in eyepiece design was very slow and not always in the right direction.
Huygens
Christian Huygens developed the first compound eyepiece in 1703. A pair of plano-convex elements contain both spherical and chromatic aberrations. Long ago, Huygens eyepieces were standard equipment with telescopes of f/15 or greater telescopes. At the longer focal ratios, these eyepieces perform marginally well, although their field of view is very narrow. They lack an overall sharpness and are considered to have poor image quality.
Huygens eyepieces are generally the least costly eyepieces on the market. Huygens eyepieces incorporate two optical elements. They perform quite well on long focus refracting telescopes, but they can show image distortion as the telescope's focal length becomes shorter. Huygens are very good for projection of solar images since they don't use cement to hold the lens elements.
Ramsden
It was Christian Ramsden who invented this eyepiece in 1783. It is similar to a Huygens in that it consists of two plano-convex lenses, except both of the convex surfaces have identical focal lengths and they face each other. In most cases the lenses are separated by two-thirds to three-quarters of their common focal length, which represents a severe compromise between eye relief and aberrations. This design was an improvement, albeit a small one. in the history of eyepiece design.
Kellner
About 65 years after the Ramsden eyepiece was developed, Carl Kellner introduced the first achromatic eyepiece in 1849. He placed a cemented two element achromat lens in place of the eye lens of the Ramsden. He also used flint glass closest to the observer's eye and crown glass in the other elements.
The design reduced most of the aberrations in Huygens and Ramsden eyepieces and had fairly good color correction and edge sharpness. They also had good field of views (about 40 to 50 degrees).
The biggest problem that plagues the Kellner design is internal reflections. Today's anti-reflection coatings make these usable, economical choices for small to medium aperture telescopes at low to medium powers.
Orthoscopic
Ernst Abbe invented the orthoscopic eyepiece in 1880, and it has become a favorite of amateur astronomers ever since. Its field lens consists of a cemented triplet matched to a single plano-convex eye lens. Orthos are close to perfect eyepieces that have excellent eye relief, nearly non-existent chromatic or spherical aberration, have a fairly flat, wide field of view (40 to 50 degrees), and have little internal reflection. Ortho eyepieces remain one of the best for nearly all amateur telescopes.
Erfle
The original wide field eyepiece was developed for the military in 1917. Because it has field of views between 60 and 75 degrees, the amateur astronomers quickly adopted it. Erfles have either five or six elements, with either two achromats with a double convex lens in between or with three achromats.
Erfle are designed to give a very wide field of view, usually from 60-70°. The Erfle is usually less expensive than the plossl's. However they can suffer from considerable image distortion near the edge of the field of view when used at high magnification. They are most useful for observing deep sky objects.
Erfles can give panoramic views of the night sky, but at the expense of image sharpness with astigmatism at the edge of the field. This design doesn't work well for lunar or planetary observations that use higher powers. They work exceptionally well at low power, wide angles.
Plossl
An optician named G. S. Plossl, living in Vienna, Austria, developed this excellent eyepiece in 1860. After a hundred years of relative obscurity, the design finally caught on and has resulted in one of the most highly regarded eyepiece designs around. Excellent on all criteria, it features twin close-set pairs of doublets for the eye lens and the field lens.
Plossl's incorporate at least 4 optical elements. The plossl design is a very well designed eyepiece, I would highly recommend them if you are using a Newtonian telescope with a very short local length. Plossl's are very costly to make and hence a lot more expensive than the other designs mentioned so far. Inexpensive plossl's usually exhibit some degree of internal reflection, which is not present in the more expensive models. Plossls generally have a wide field of view and generous eye relief. If there is such a thing as a good all around eye piece for observing then these are it: planet viewing, lunar observing or for deep sky objects.
In 1980, Al Nagler, owner of Tele Vue Optics, Inc., introduced a line of Plossls that are considered almost legendary today. This set up a cascade of companies that developed and marketed their own line of outstanding Plossls. Some are better than others and it's fair to say that you get what you pay for. Things to look for when purchasing Plossls include, fully multi-coated optics, blackened lens edges, and anti-reflection threads for filters.
Zoom
I include this type, because the beginning amateur astronomer is often tempted to buy one of these eyepieces thinking that it will replace several individual eyepieces. But the truth is its too good to be true unless you pay for the premium quality parfocal designs. These are EXPENSIVE. Resist all urges to purchase cheaper versions.
Advanced Types
Other types include Brandon, Lanthanum LV, Wide-Field, Nagler, Panoptic, Super Plossl, Super Wide Angle, Ultra Wide Angle, Standard Ultima, Wide Field Ultima, Extra Low Ultima, MegaVista, and Ultrascopic. All of these high-end eyepieces deserve careful research by potential buyers, and are recommended depending on the type of application.
Various improved designs incorporating 6 to 8 lens elements boast apparent fields up to 85°-so wide you have to move your eye around to take in the whole panorama. Light transmission is slightly diminished, but otherwise the image quality in these eyepieces is very high. So is their price.
Barlow Lens
A Barlow lens isn't actually an eyepiece, it simply multiplies the amount of magnification of the eyepiece. Barlows come in 1.5X, 2.0X, 2.5X and 3.0X. Barlows are mostly used for planetary and binary star observation. Barlows must be of high quality though or the resulting image will be badly distorted.
Summary
If you're looking to purchase an eyepiece now, I can tell you that I have had remarkable success purchasing high-grade Tele Vue, Nagler and Meade Series 4000 Plossls from the online auction service eBay. Try searching on "eyepiece", "televue", "tele vue", "Meade", "Celestron", and mispellings like "telvue" or "mead". With patience and timing, you can put together a decent cross section of magnifications with quality eyepieces at a fraction of the new cost... Something to consider if you haven't won the Lotto.
Before deciding if you actually need to clean your optics, read these instructions ALL of the way through first. Here are two very informative articles on how to clean mirrors, eyepieces and filters. These are in the "Must Read" category if you are thinking about cleaning your optics!!
UNDER NO CIRCUMSTANCES SHALL ANY USER OF THESE INSTRUCTIONS HOLD KRAFTYWERKS.COM OR THE MANUFACTURERS OF ANY PRODUCT MENTIONED HERE LIABLE FOR ANY DAMAGE THAT MAY OCCUR, DIRECTLY or INCONSEQUENTIALLY, WHATSOEVER.
[This means that you can really screw up, big time, and it'll be your fault, if you're not VERY careful...]
This file is an elaboration of a message sent in response to a request for help on ASTROFORUM in January, 1987. It is presented as an effort to assist those who have never had occasion to perform this delicate task. The best advice on cleaning mirrors and lenses is ... you guessed it... DON'T. But if things are so bad that you must, do it as follows:
FOR MIRRORS
Blow all loose dirt off with "Dust Off" or another canned clean air product. Take care not to shake the can while you are using it, and be sure to release a little air before using it on the optical surface. This will assure that no liquid is dispensed to make things worse!
Prepare a VERY dilute solution of mild liquid detergent (Dawn) Rinse the mirror off under a moderate stream of lukewarm water.
Make a number of cotton balls from a newly opened package of Johnson & Johnson sterile surgical cotton, U.S.P. Soak 2 or 3 balls in the detergent solution. Wipe the surface of the wet mirror. The only pressure on the cotton should be its own weight.
Throw cotton balls away.
Repeat process with new cotton balls, using a LITTLE more pressure.
Rinse mirror thoroughly under tap, which has been kept running for this step.
Rinse mirror with copious amounts of distilled water (do this no matter how clean your tap water is).
Set mirror on edge to dry, using paper towels to absorb the water which will all run to bottom of mirror. Keep replacing paper towels.
If any beads of water do not run to bottom, blow them off with Dust Off.
Replace mirror in cell, being careful to keep all clips and supports so loose that the mirror can rattle in the cell if it is shook. (Perhaps .5 to l mm clearance).
Spend the next month realigning your scope.
If you do anything more than this, you will damage the coating, and maybe the glass.
FOR OBJECTIVE LENSES
DO NOT UNDER ANY CIRCUMSTANCES REMOVE A LENS FROM ITS CELL, OR THE CELL FROM THE TELESCOPE.
This restriction means that the above procedure must be modified. Only the front surface can be cleaned. If you remove the cell from the telescope, you will be in big trouble. There are probably not more than 25 people in this country who can effectively collimate a refractor!
Blow loose dirt off with Dust-Off, using the above precautions.
Soak the cotton balls in a 50:50 solution of Windex and water. Squeeze slightly so that the balls are not dripping wet.
Wipe front lens surfaces with the wet cotton. Follow immediately with dry cotton, using little or no pressure.
Repeat procedure, using slightly more pressure.
If some cotton lint remains on surface, blow off with Dust-Off.
Repeat procedure if lens is not clean, but if one repeat does not do it give up and leave it as is. Inspect lens to make sure that no cleaning solution has found its way into the lens cell, or between the elements. If this has happened, leave the telescope with the lens uncovered in a warm room until it is dry.
FOR EYEPIECES AND BARLOWS
Follow the procedure given for objective lenses, but use Q-Tips (with plastic sticks) instead of cotton balls. You may, of course, clean both surfaces. The eyebrow juice on the eye lens of eyepieces may require repeated applications. I think that this is OK in this case.
SOME DONT'S
Do not use any aerosol spray product, no matter who sells it, or what their claims are.
Do not use lens tissue or paper. It DOES scratch.
Do not use pre-packages cotton balls, they frequently are not cotton.
Do not use any kind of alcohol.
Do not use plain water.
Do not use any lens cleaning solution marked by funny companies, like Focal, Jason, Swift, or even Edmund's. Dawn and Windex are cheap and commonly available.
GENERAL GUIDELINES FOR CLEANING OPTICS AND MIRRORS
NOTE: These guidelines have been synthesized from several different sources from experienced astronomers to optics manufacturers. Although no one cleaning method or cleaning solution works for all surfaces, optical coatings or types of contamination, these guidelines apply to most commercially available optical surfaces and contaminates.
Since these guidelines are highly dependent your actual application to your optics, the purity and type of materials used or type of contamination present so...
UNDER NO CIRCUMSTANCES SHALL ANY USER OF THESE INSTRUCTIONS HOLD KRAFTYWERKS.COM OR THE MANUFACTURERS OF ANY PRODUCT MENTIONED HERE LIABLE FOR ANY DAMAGE THAT MAY OCCUR, DIRECTLY or INCONSEQUENTIALLY, WHATSOEVER.
Most of the components cited here are generally available from your local drugstore, pharmacy or optical supply company. Some of the more advanced solvents must be obtained from chemical supply houses.
WARNING: When in doubt as to whether to clean your optics or if you are unsure of the quality and purity of your cleaning components or your cleaning technique, DO NOT PROCEED!
The cleaning of optical surfaces, especially those of first-surface mirrors, is the most delicate and exacting task which the astronomer is called upon to perform. At the time of cleaning, a lens is most vulnerable to damage that can not be repaired.
Yet, if a telescope is to perform at its greatest potential, cleaning must be done time to time. First you must realize that usually the best advice on cleaning mirrors and lenses is this: DON'T DO IT unless absolutely necessary!
With this said, let's proceed.
DUST
Most dust that you see on your objective lenses, mirrors, correcting plates, eyepieces or filters is harmless and generally does not effect the quality of your optics or effect image quality, whatsoever. This dust should be left-alone or simply blown-off with high-quality compressed air product that uses dry nitrogen as its propellant. DO NOT use compressed air products that contain solvents as their propellants!
Most compressed air products designed for blowing off electronics or computers contain such solvents. Do not use any other type of aerosol product that claims to clean glass of any type no matter what the claim of the manufacturer. If dry nitrogen propelled air is not available, the use of a compressed air product sold at photography stores such as Dust-Off may be used if your are careful not to tilt the can, thereby releasing the propellant onto your optical surface.
Alternatively, you may obtain a rubber syringe bulb (found in the baby supply section of your local grocery store or pharmacy) or a blower bulb/camel hair brush combination from a local photography supply store. Blow the dust off starting at the center of lens or mirrors working your outward towards the outer edge.
Stubborn dust particles can be ever so gently brushed outward using the same method only using a soft camel hair brush. If you observe anything other than dust (sand particles or eyelashes, for instance) DO NOT BRUSH THEM for they will scratch your optics!
DIRT, FINGERPRINTS, BUGS and other CONTAMINATES
Dirt, sand particles, grease, fingerprints, bugs or other contaminates that adhere to the surface of mirrors and lenses may degrade image quality, but they will not damage the delicate optical surface until they are moved against it.
Certain organic residue or oils from fingerprints or bugs or cigarette smoke may eventually damage delicate coatings and must be cleaned. Removing dirt without allowing it to rub against the underlying optical surface is what makes cleaning such a critical task.
If your mirrors and lenses are so dirty that they must be cleaned, then proceed carefully as instructed.
PREPARE CLEANING SOLUTION
Many types of powerful commercial solvents are available including methyl ethyl ketone (MEK), methylene chloride (MEC), acetone or pure isopropyl alcohol, but these products should only be used by professionals in the correct dilution on the appropriate optical surface.
However, most professional observatory operators say the simplest solution is the best! Click here to see what they say at the Gemini Observatory in Hawaii.
For personal use, you should prepare a solution that can be used safely on all optical surfaces based upon commonly available ingredients as follows:
1. Distilled Water. The basis of this solution is the most commonly available solvent on the planet (which also happens to also be responsible for life on earth): water. In our case, pure distilled, de-ionized water. Do not use tap water or bottled water for this purpose because they both contain minerals and other contaminates that defeat the purpose of what we are trying to accomplish: PURITY.
2. 99%-97% Isopropyl Alcohol. You may have to ask your pharmacist for this or look around your drugstore. Most off-the-shelf "isopropyl" alcohol is usually in the 70%-90% with the other 30%-10% containing regular water or other contaminates. Avoid this. Methyl hydrate (methanol) may be substituted for isopropyl alcohol.
3. Mild Detergent. Liquid dish detergent that is fragrance-free, color-free works best such as Dawn or other similar product (hint: the folks at Gemini say use horse shampoo!).
4. New plastic spray bottle. These can usually be found in the garden supply section of your local Wal-Mart or garden supply store. Do not be tempted to use a used bottle that previously contained some other solution such as glass cleaner, buy a new bottle; it only cost a couple of bucks. A one time solution can be mixed in a clean drinking glass, in a pinch, that has been adequately rinsed in distilled water.
Now the recipe. If you are cleaning a Newtonian type reflector you will be cleaning your primary and secondary mirrors. If they are aluminized mirrors (most are) do NOT add the isopropyl alcohol in step 3, below because alcohol reacts with aluminum.
If you are cleaning a refractor or SCT you will be primarily cleaning your objective lens or front corrector plate, do add the alcohol in step 3. On occasion, SCT and other catadioptric telescope owners will want clean their primary or secondary mirrors, these are usually aluminized as well.
You will need to mix two solutions, one with alcohol and one without, carefully marking each bottle as required with an "M" for mirror and a "G" for glass.
1. First start by rinsing your new, unused spray bottle with the distilled water. Fill and vigorously shake the water in the bottle at least three times to remove any inadvertent particles or residue that may be present in the bottle as a result of manufacturing.
2. Next, fill 3/4 of the bottle with the distilled, de-ionized water.
3. For glass cleaning only add 1/8 of the bottle with 99% isopropyl alcohol. Too much alcohol will leave streaks. This should leave the bottle 1/8th empty. For mirror cleaning omit the alcohol or any other solvent besides the mild liquid soap.
4. Finally, very carefully add 2-3 drops of the mild dish detergent. If your detergent bottle dispenses too much use an eye dropper. Too much soap will leave a cloudy residue.
Screw on the pump spray top immediately to avoid dust or other particulate material from entering the solution. Always keep it covered, in a cool dark place when not in use. Do not refrigerate.
WARNING: Care should be taken not to inadvertently get this solution on any other part of your telescope except the optical surfaces. Lens cells and corrector plates are often held in place by cork or rubber seals and gaskets to which this solution could damage. Always blot or wipe excess solution and prevent it from running down in these areas or entering the optical tube assembly.
CLEANING MATERIALS
You will need to obtain several different cleaning materials depending on whether you are cleaning mirrors, lenses or eyepieces. First and foremost, never use prepackaged bulk "cotton" balls, they always contain other miscellaneous fibers that can scratch delicate coatings and secondly they are not very absorbent.
Additionally, also never use tissues, toilet paper, paper towels or lens cleaning paper that you may find at the photo store. All of these products may scratch coated optics or leave more dust than they remove. For lenses and mirrors, we recommend the use of precision quality optical wipes such as Opto-Alignment Technologies Inc.'s OPTO-WIPES(tm) available from AOS.
Additionally, wearing OPTO-GLOVES(tm), also made by the same manufacturer, will prevent recontamination from fingerprints and body oils. If OPTO-WIPES are not available, obtain Johnson & Johnson's Sterile Surgical Cotton, (U.S.P.) which is sold in bulk pads at your local pharmacy.
The pro's say to use a Natural Sponge! You will also need pure cotton swabs (Q-tips), that are mounted on the plastic sticks rather than the wood or paper sticks to clean your eyepieces and filters.
DISASSEMBLING YOUR TELESCOPE
Many factors must be considered before attempting to disassemble your telescope. Always consult your manufacturer or your operating manual prior to disassembling any telescope. Disassembly may also void your warranty, check to be sure. Additionally, disassembling your scope can also cause it to be permanently out of alignment (collimation) requiring it to be returned to the factory for correction.
This can be both time-consuming and expensive! Some types of scopes, such as Newtonian reflectors, require special tools or collimation devices to re-align the optics, make sure you have these on-hand prior to disassembly. In general, avoid disassembling your scope unless absolutely necessary!
There are many user groups and experienced amateur astronomers that can give you good advice in this area for your particular scope, so we will not go into specific details regarding this process in these guidelines. In general, consider the following:
1. Refractor. Most refractor telescopes have multiple objective lens systems that are permanently mounted in cells or are permanently attached to the optical tube assembly (OTA). Because of their closed optical tube design, only the exposed surface of these optics will ever need to be cleaned.
Again, most refractors do not have user "collimatable" optics and must be returned to the factory for optical alignment. Never disassemble a lens cell, under any circumstance, while many are air-spaced, others are vacuum sealed or filled with an inert gas such as nitrogen or even oil!
2. Catadioptric. Schmidt-Cassegrain, Maksutov-Cassegrain, Schmidt-Newtonian, Ritchey-Cretien and other similar telescopes employ multiple optical surfaces that must be perfectly aligned for correct collimation. For simplicity sake we will refer to these as CATs.
Most telescopes of this type generally have closed optical tubes assemblies minimizing any debris that can enter into the OTA except through the visual port. Although these telescopes are usually user collimatable, the front correcting plates are rotationally figured and aligned to perfectly match their primary mirrors.
Care must taken to precisely mark the position of each component prior to disassembly as well as taking care not to drop screws or the secondary mirror down onto the primary mirror causing permanent damage. Again, disassembly of these scopes is not recommended, except by experienced personnel.
Material (such as bugs or dust) can sometimes enter inside the optical tube assembly or debris can be seen on the secondary mirror. These items can usually be carefully vacuumed out by attaching a long drinking straw to a vacuum cleaner hose and gently inserting it into the back of the telescope through the visual port to suck the debris or critter out without disassembling the scope. Like refractors, usually only the exposed surface of the front correcting plate need ever be cleaned.
3. Newtonian/Dobsonian/Truss-type reflector. The mirrors of these scopes are the most susceptible to accumulating dirt and dust because of their open, exposed design. But, these scopes are also the easiest to disassemble and clean as well as put back together and collimate.
Again carefully marking the positions of the secondary and primary mirror will promote successful reassembly. Also, as previously advised, care must be taken not to drop components and fasteners down the optical tube onto your primary mirror.
CLEANING MIRRORS
1. Mirrors usually have to be removed from their optical tube assembly (OTA) prior to cleaning. As stated above, this is usually not recommended except for Newtonian telescopes. Aluminized mirrors should only be cleaned once a year. Further cleaning will degrade the optical surface. Care should always be taken not to drop your mirror while cleaning or otherwise bump it with other items in the area. If cleaning your mirror in the kitchen sink place some towels or other material in the sink (not obstructing the drain, of course) to cushion the mirror in case it slips.
2. Before any cleaning operation, always blow all loose dirt off with a compressed air product prior to proceeding. Take care not to shake the can or tilt it while you are using it and be sure to release a little air before applying it to the optical surface. This will assure that no propellant is dispensed onto the mirror. You can also use the rubber syringe bulb for this purpose, though it is not as effective. Blow the particulate matter from the center of the mirror outwards towards the edge of the mirror and eventually off it.
3. Rinse the mirror off under a moderate stream of lukewarm water for two or three minutes. Test the temperature of the water with your wrist, just as you would when warming a baby's bottle. Allow the water to run at this temperature during the entire cleaning process.
4. Spray the entire mirror surface with your cleaning solution. If you made your solution in a cup instead, tear a swatch of cotton from your newly opened package of Johnson & Johnson sterile surgical cotton, soak the swatch in the cleaning solution and squeeze the solution onto the mirror surface.
5. First, we want to remove any visible solid particulate matter from the mirror surface by using the Opto-Wipes or small cotton balls torn from the surgical cotton. Starting at the perimeter of the mirror and spiraling around toward the center of the mirror, gently blot the Opto-Wipe (or cotton ball) onto the particles lifting them off the mirror surface. The Opto-Wipes are specifically designed to accomplish this feat. Replace the wipe or cotton ball with each and every blot and discard until all visible particles have been lifted off the mirror surface.
6. Next, re-wet the mirror surface with the cleaning solution or soak more cotton balls. Begin gently wiping the wet mirror surface, again starting at the circumference and spiraling your way towards the center using absolutely no pressure on the wipe. The only pressure applied should be that of the weight of the wipe or soaked cotton balls. Change wipes or cotton balls often, after each short stroke and discard.
7. Rinse the mirror with copious amounts of distilled water. Visually inspect the mirror surface for stubborn spots or splotches that were not removed by steps 5 or 6.
8. If particulate matter is still present repeat step 5. If organic splotches are still present repeat step 6 using ever so slightly increased pressure. Repeat step 7. DO NOT REPEAT AGAIN. If particles still remain, they are probably embedded in the mirror surface and have to be removed professionally.
9. Once the mirror has been thoroughly rinsed with the distilled water, turn it upon it's side for the excess water to drain. Then use the clean Opto-Wipes to blot the excess water and the compressed air to chase away the remaining droplets. Do not use dry cotton, as it may leave behind dust or threads.
10. Replace the mirror into the telescope, loosely applying the retaining clips enough to gently hold the mirror and follow your manufacturer's instructions for optical realignment.
OBJECTIVE LENSES AND CORRECTOR PLATES
WARNING: Never remove a refractor's objective lens or remove the objective lens from their cell under any circumstances! Only remove an SCT's corrector plate under extreme circumstances and only after carefully marking its rotational position in relation to the optical tube assembly. This procedure will assume that only the front surface of either a lens or corrector plate is being cleaned and that it is still attached to the telescope.
1. Blow off all dust from the lens or plate as described above, working from center outward until all particles that can be removed, are removed.
2. Apply cleaning solution to the Opto-wipes or surgical cotton balls squeezing and discarding any excess solution. Never apply or directly spray the lens or corrector plate which could cause the solution to drip down into the cork or rubber gaskets and enter the optical tube assembly.
3. Gently blot any visible solid particulate matter, lifting it off the glass surface, being careful not to apply any lateral motion in the process which could resulting in scratching the glass surface or its coatings. Discard each wipe or cotton ball with each and every blot and discard.
4. Next reapply cleaning solution to wipes or cotton balls and begin working your way from the center outward like spokes on a bicycle. The only pressure being that of the weight of the wipe or cotton ball itself. Replace and discard each wipe or cotton ball with each spoke as your proceed around the entire glass surface.
5. Examine the glass surface for stubborn particles or organic splotches that were not removed by step 4. If particles or spots remain, repeat step 4 gently, using slightly more pressure.
6. Once complete, use a dry Opto-Wipes or cotton balls and repeat the spoke pattern, drying up any excess moisture, again replacing each wipe or cotton ball as your proceed.
7. Blow off any excess dust that may have been left by the cotton balls or that attached from the air onto the moist surface using the compressed air.
EYEPIECES, BARLOWS, TELESCOMPRESSORS
Follow the procedure given for objective lenses, but use Q-Tips (cotton on plastic sticks) instead of cotton balls. You may, of course, clean both surfaces. The eyebrow sweat on the eye-ward surface of eyepieces may require repeated applications.
FILTERS
Some filters that use diachronic, gel, or metal coatings (such as Solar filters) or those made of plastic may not react well to the presence of alcohol or other solvents in the cleaning solution, so mix a small batch of the solution as directed for cleaning mirrors (distilled water and soap). Then follow the cleaning procedure as described for objective lenses.
My Reading List
To set the record straight, he debunks these and many other astronomy-related urban legends in this knowledgeable, lighthearted volume. The early chapter "Idiom's Delight" sets the stage by clearing up the scientific inaccuracies in everyday expressions as in the phrase "light years ahead," for example, which is used to indicate timeliness or prescience when light years are actually a unit of distance.
In later chapters, Plait explains meteors, eclipses, UFOs, and the big bang theory, revealing much about the basic principles of astronomy while clearing up fallacies. With avuncular humor, he points out the ways advertising and media reinforce bad science and pleads for more accuracy in Hollywood story lines and special effects.
This book is the first in Wiley's Bad Science series on scientific misconceptions (future titles will focus on biology, weather and the earth). (Mar.)Forecast: If every entry in the series is as entertaining as Plait's, good science may have a fighting chance with the American public. Expect respectable sales, for the paperback format is nicely suited for armchair debunkers.
The photos and paintings in this edition are beautiful and complement the text perfectly. The structure of the book follows the content elegantly, and the prose is lucid. It is a pity that Carl Sagan is no longer at hand to speak to the newest generation of humans; I wonder what his clear voice would have to say about the newest findings in astronomy, and about the newest happenings in our world.
This book is a reminder of our heritage, sometimes brighter than we now can know, sometimes dark enough to chill our souls with the thoughts of the evils committed by our ancestors. It is a warning too, for it reminds us that we have the frightening technology to destroy ourselves. But it is also a beacon of hope, for it reminds us that we have the choice of whether to allow our civilization to fade into obscurity, or to settle our earthly differences and commit ourselves to our best destiny, a future among the stars.
Casting a wide net through history and culture, Sagan examines and authoritatively debunks such celebrated fallacies of the past as witchcraft, faith healing, demons, and UFOs. And yet, disturbingly, in today's so-called information age, pseudoscience is burgeoning with stories of alien abduction, channeling past lives, and communal hallucinations commanding growing attention and respect.
As Sagan demonstrates with lucid eloquence, the siren song of unreason is not just a cultural wrong turn but a dangerous plunge into darkness that threatens our most basic freedoms.
In contrast, a set of articles about the Sun leaps forward into the 1990s, and as the collection continues with columns about observing the Moon, planets, comets, and stars, it seems to indicate that these two decades were pivotal ones for amateur sky gazers. Carlson provides fascinating assessments of both how much and how little was known 50 years ago, and he charts the evolution of theories and the rise and resolution of controversies, thus offering invaluable insights into the history of scientific thought and methodology.
Technically precise yet always clear, these popular science columns remain vital and exciting. Donna Seaman
Mapping the Sky has maps of major southern and northern constellations for each month of the year. The Star Guide is a concise but complete astronomy guide. Both books come with full color photographs and charts.
The kit comes accomodated in a beautiful box so you can carry it everywhere. It is an ideal kit for your nightsky watching sessions. A great buy!
An essential guide to understanding and appreciating the Universe, Visions of the Cosmos builds on the success of the authors' previous book, Hubble Vision, which became an international best-seller and won world-wide acclaim. Carolyn Collins Petersen is a science journalist and creator of educational materials for astronomy. She is the former Editor of Books & Products at Sky Publishing Corporation, and served as Editor of SkyWatch and Associate Editor of Sky & Telescope magazines.
Petersen is the lead author of the book Hubble Vision, first published in 1995 by Cambridge University Press, and co-written with Dr. John C. Brandt. She is also co-editor (with J. Kelly Beatty and Andrew Chaikin) of The New Solar System, fourth edition, co-published by Sky Publishing Corporation and Cambridge University Press. John C. Brandt has held positions as a research scientist, teacher, and administrator, and is currently an adjunct professor of physics and astronomy at the University of New Mexico.
He served for 20 years as Chief of a major NASA scientific laboratory and was the Principal Inverstigator for the Goddard High Resolution Spectograph on the Hubble Space Telescope. John received the NASA Medal for Exceptional Scientific Achievement in 1978 and 1992, and has had a minor planet formally named after him (3503 Brandt) for his fundamental contributions to understanding of solar system astrophysics.
Most of the features discussed are visible to the naked eye and all can be seen with a small telescope or binoculars. Ian Ridpath has been a full-time writer, broadcaster and lecturer on astronomy and space for more than twenty-five years. He has written and edited more than 40 books, including A Comet Called Haley (Cambridge, 1985). Wil Tirion made his first star map in 1977.
It showed stars to the magnitude of 6.5 and was issued as a set of maps by the British Astronomical Association in 1981. He has illustrated numerous books and magazines, including The Cambridge Star Atlas (Cambridge, 2001). Previous Edition Pb (1999): 0-521-66771-2
Superstring theory has been called "a part of 21st-century physics that fell by chance into the 20th century." In other words, it isn't all worked out yet. Despite the uncertainties--"string theorists work to find approximate solutions to approximate equations"--Greene gives a tour of string theory solid enough to satisfy the scientifically literate.
Though Ed Witten of the Institute for Advanced Study is in many ways the human hero of The Elegant Universe, it is not a human-side-of-physics story. Greene's focus throughout is the science, and he gives the nonspecialist at least an illusion of understanding--or the sense of knowing what it is that you don't know. And that is traditionally the first step on the road to knowledge.
Professor Hawking transformed our view of the universe in his landmark bestselling book A Brief History of Time, and most recently in the bestselling Universe in a Nutshell. Here he reviews ideas about the universe from Aristotle to Newton and Einstein, applying the principle of quantum mechanics to the Big Bang, black holes, and the universe's ultimate fate.
He goes on to advance a "no boundary" theory of time and space that could lead to one unified theory and a true understanding of our universe. The Theory of Everything presents the most complex theories, both past and present, of physics; yet it remains clear and accessible. It will enlighten readers and expose them to the rich history of scientific thought and the complexities of the universe in which we live.
One of the most influential thinkers of our time, Stephen Hawking is an intellectual icon, known not only for the adventurousness of his ideas but for the clarity and wit with which he expresses them. In this new book Hawking takes us to the cutting edge of theoretical physics, where truth is often stranger than fiction, to explain in laymen’s terms the principles that control our universe.
Like many in the community of theoretical physicists, Professor Hawking is seeking to uncover the grail of science — the elusive Theory of Everything that lies at the heart of the cosmos. In his accessible and often playful style, he guides us on his search to uncover the secrets of the universe — from supergravity to supersymmetry, from quantum theory to M-theory, from holography to duality.
He takes us to the wild frontiers of science, where superstring theory and p-branes may hold the final clue to the puzzle. And he lets us behind the scenes of one of his most exciting intellectual adventures as he seeks “to combine Einstein’s General Theory of Relativity and Richard Feynman’s idea of multiple histories into one complete unified theory that will describe everything that happens in the universe.”
With characteristic exuberance, Professor Hawking invites us to be fellow travelers on this extraordinary voyage through space-time. Copious four-color illustrations help clarify this journey into a surreal wonderland where particles, sheets, and strings move in eleven dimensions; where black holes evaporate and disappear, taking their secret with them; and where the original cosmic seed from which our own universe sprang was a tiny nut.
These observations have confirmed many of Professor Hawking's theoretical predictions in the first edition of his book, including the recent discoveries of the Cosmic Background Explorer satellite (COBE), which probed back in time to within 300,000 years of the universe's beginning and revealed the wrinkles in the fabric of space-time that he had projected.
Eager to bring to his original text the new knowledge revealed by these many observations, as well as his most recent research, for this revised and expanded edition Hawking has prepared a new introduction to the book, revised and updated the original chapters throughout, and written an entirely new chapter on the fascinating subject of wormholes and time travel.
In addition, to heighten understanding of complex concepts that readers may have found difficult to grasp despite the clarity and wit of Hawking's writing, this edition is magnificently enhanced throughout with more than 240 full-color illustrations, including satellite images, photographs made possible by spectacular new technological advances such as the Hubble telescope, and computer- generated images of three- and four-dimensional realities.
Detailed captions clarify these illustrations, enabling readers to experience the vastness of intergalactic space, the nature of black holes, and the microcosmic world of particle physics in which matter and antimatter collide.
A classic work that now brings to the reader the latest understanding of cosmology, The Illustrated A Brief History of Time is the story of the ongoing search for the tantalizing secrets at the heart of time and space.
Einstein's book is not casual reading, but for those who appreciate his work without diving into the arcana of theoretical physics, Relativity will prove a stimulating read.
The print version consists of more than 3,000 entries, of which 630 are primary articles discussing important theoretical and observational results of astronomical research, including entries as varied as Climate, Galaxies, Jupiter, and Telescope engineering. The work is especially strong in its coverage of topics related to the sun and solar physics. All of these lengthy articles provide both an overview and state-of-the-art review of the subject matter. Each includes at least three illustrations and a bibliography of relevant print and Web resources.
In addition to the primary articles, the work contains almost 800 short topical articles providing key definitions and background information. There are also 290 articles detailing specific space vehicles and missions, 280 entries for observatories, 650 short biographies, and one entry for each of the 110 Messier objects. Although the encyclopedia is aimed at readers of all levels, it is definitely a scholarly work and will be most useful for college students and professionals in the field. Many of the entries require the use of differential calculus to fully understand the subject matter. In addition to the entries, cross-references and a detailed subject index are provided.
The heart of the online version is the text of the print version. Users find information by browsing by article title, subject, or contributor or searching by keyword. Cross-references are hypertext linked so that the reader may easily jump within an entry or from article to article. Bibliographies are also linked to full-text sources to which a library subscribes. In addition to the text of the print encyclopedia, the online encyclopedia provides links to astronomical Web sites, recent news related to astronomy and space exploration, and special feature articles on topics of current interest. There are plans to add new functionalities; for example, a recent enhancement allows users to personalize the site by bookmarking articles or figures, saving searches, and more. The Web version will be updated quarterly, but not enough time has passed since release for an update to be evaluated.
Unfortunately, the online version of the encyclopedia offers a variety of problems. During the course of this review, the Web site was consistently slow to respond. More seriously, the typographic codes used to produce the print edition have not translated well into the Web environment. Headings with embedded punctuation or dates, including all biography entries, become confusing and difficult to read. For example, the heading for Carl Sagan is Sagan, Carl Edward (1934–96). The links to full-text resources are frustrating when the subscriber to the encyclopedia is not also a subscriber to the source for the full text. These links create the illusion that information will be available that is not really there for most users. The links to outside sources are useful, but these Web sites may also be discovered using standard search engines, although the encyclopedia organizes them nicely. Although there is a Help button, no help is available at this time, unless the user sends an e-mail query. Fortunately, the search software is straightforward and requires little assistance for any experienced Web user.
As a print resource, Encyclopedia of Astronomy and Astrophysics is a valuable tool that will become the standard source of its type in academic and research collections. The quality of the online version will undoubtedly improve over time. Institutions that support astronomical research will probably wish to subscribe to the online version, despite its current drawbacks. Other libraries will be satisfied with the one-time purchase of the print edition. RBB
Copyright © American Library Association. All rights reserved
Including a bonus 2-hour DVD containing rare archival footage and newsreels, In Their Own Words: The Space Race utilizes vintage vivid documentary and narrations, revealing interviews, and audio clips of Presidents and pilots alike to chronicle all 17 Apollo missions, including the pioneering Mercury and Gemini programs. From blastoff to splashdown, you are there, experiencing Neil Armstrong's lunar "leap for mankind" and the shocking suspense of Apollo 13. America's space program reverberates thrillingly throughout the In Their Own Words collection.
Rediscover the most groundbreaking moments in the history of space exploration with documentary footage and narration, candid interviews and the actual transmissions between Mission Control and crews of the Apollo, Mercury, and Gemini projects.
CD 1: The Beginning of the Dream: Project Mercury
CD 2: Gemini Ups the Stakes
CD 3: Race to the Moon
CD 4: The Triumph of Apollo 11
CD 5: Laughs from the Moon: Apollo 11 and 12
CD 6: "Houston, we have a problem"
CD 7: Apollo 14, 15, 16, 17 and the .Legacy of Apollo
*Race to the Moon
Features rare archival footage, documentaries, and an interview with Wernher von Braun, "father" of the Apollo program.
ElWampas AstroPhotography
