• The September equinox and the first quarter moon both fall on September 22 this year. In 2012, the moon reaches its half-lit first quarter phase only about five hours after this year's September equinox.
• The equinox happens today at 14:49 Universal Time, which is 9:49 a.m. Central Daylight Time for us in the central U.S. The September equinox takes place whenever the sun is at zenith - straight overhead - at the Earth's equator. This magical moment signals the beginning of autumn in the Northern Hemisphere and spring in the Southern Hemisphere. On the day of an equinox,

the sun rises due east and sets due west all over the world.
• What's the image at the top of this post? It shows the descent of the snake on the day of an equinox at Chicen Itza in the Mexican state of Yucatán. On the spring and autumn equinoxes, in the late afternoon, the northwest corner of the pyramid casts a series of triangular shadows against the western balustrade on the north side that evokes the appearance of a serpent wriggling down the staircase.
• To celebrate the change of seasons, enjoy the moon on this, the first evening of a Northern Hemisphere autumn - or Southern Hemisphere spring. Everyone around the world will see the moon at or in close vicinity of first quarter phase as the sun sets tonight. Any first quarter moon that happens to fall on the day of the September equinox will also show you where the sun is positioned in front of the constellations

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