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Harvest Moon

September 11, 2011

One of the most popular astronomical events of the year is coming up the next couple of nights: the Harvest Moon — the full Moon that’s closest to the autumnal equinox, which is coming up on September 23rd. The time of the full Moon is 4:27 a.m. Central Time tomorrow, so you can look at both tonight and tomorrow night as Harvest Moon nights.

One reason for the “Harvest Moon” moniker is that this full Moon occurs around the end of the growing season for much of the northern hemisphere, so it’s time to harvest the crops. But another reason is that the light of the full Moon actually helps farmers bring in summer’s bounty.

At this time of year, the full Moon rises only a few minutes later each night for those at mid to high northern latitudes — northward of about 40 degrees. In fact, from some locations, the Moon can actually rise a tad earlier each night for several nights in a row. This gives farmers extra light, extending the harvest time well into the night.

Over the course of a year, though, the Moon rises an average of about three-quarters of an hour later each day. So if it’s rising only a few minutes later right now, it has to make up for that time somewhere else — in this case, around the time of new Moon toward the end of the month. Then, the Moon rises well over an hour later each day as seen from those same high latitudes. It’s a delay that balances the celestial books on the Harvest Moon.


Script by Damond Benningfield, Copyright 2011


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