Calendar

Bring your sunglasses this year! The peak of the Perseids (100 meteors per hour) happens smack dab on the full moon, so you might have to squint to see any trails…

The date (in the northern hemisphere) when night and day are nearly of the same length and Sun crosses the celestial equator (i.e., declination 0) moving southward (in the northern hemisphere).

http://scienceworld.wolfram.com/astronomy/AutumnalEquinox.html