Edmund — the astronomer

A sectary astronomical

EDGAR (asks Edmund)
How long have you been a sectary astronomical?

Although Edmund is only feigning an interest in the stars, in fact he is quite knowledgeable about astronomy as an earlier passage shows:

EDMUND
This is the excellent foppery of the world, that, when we are sick in fortune, — often the surfeit of our own behavior, — we make guilty of our disasters the sun, the moon, and the stars: as if we were villains by necessity; fools by heavenly compulsion; knaves, thieves, and treachers, by spherical predominance; drunkards, liars, and adulterers, by an enforced obedience of planetary influence; and all that we are evil in, by a divine thrusting on: an admirable evasion of whoremaster man, to lay his goatish disposition to the charge of a star! My father compounded with my mother under the dragon's tail; and my nativity was under Ursa Major.

The most interesting thing here is Edmund's last sentence because it presents an opportunity to check him out as an astronomer. The dragon's tail obviously refers to the constellation of Draco (the dragon). Ursa Major (the big bear) and Draco are next to each other in the sky and both pass over Britain and thus passed over Edmund when he was both conceived and born. He is therefore quite accurate when he says he was born under Ursa Major. These days he would simply say his Zodiac sign is Leo the Lion.

But how does Edmund know which stars he was conceived under? He simply determines the constellation that was (and always is) overhead nine months before Ursa Major. He waits until Ursa Major is directly overhead. After a little mental calculation he works out that he need only wait six hours and then look overhead to see what constellation is there. He finds that it is Draco the dragon or more precisely, the dragon's tail. And so we discover that Edmund is a competent observational astronomer.