• When will we see the Harvest Moon in 2012?
• And the answer is … tonight! Over the years, we've seen lots of informal uses of

the term Harvest Moon. Some people will call all the full moons of autumn by that name. And so they should. In autumn, the time of moonrise is close to the time of sunset for several evenings in a row, around the time of full moon. It's as if there are several full moons during each autumn month.
• So for example the moon you might have seen last night, September 28, looked very full and round in the sky. Did you call it a full moon? Did someone say it was the Harvest Moon? It probably looked like one!
• Astronomers are scientists, though,

and it's no surprise that, to them, the term "full moon" or the name "Harvest Moon" means something very specific. To astronomers, the Harvest Moon is the full moon closest to the September equinox, and full moon comes at the instant when the moon is 180o from the sun in ecliptic - or celestial - longitude.
• What is the ecliptic?
• In 2012, this equinox takes place on September 22. The closest full moon to the autumn equinox reaches the crest of its full phase on September 30 at 3:19 Universal Time. That means the moon turns exactly full for us in the continental U.S. before midnight tonight, on Saturday, September 29. By U.S. clocks, that's 11:19 p.m. Eastern Daylight Time, 10:19 p.m. Central Daylight Time, 9:19 a.m. Mountain Daylight Time or 8:19 a.m. Pacific Daylight Time.

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