Every year a full phase moon closest to the Autumn Equinox (September 22nd), is termed the “Harvest Moon”. This expression was coined in the early days by which harvesters could still reap under the light of a full moon, among other sayings. The Harvest Moon basically is termed as the first full moon of the Fall season, although actually this year 2013 it is also the last full moon of the Summer season. This summer had 4 full moons rather than 3, with the September full moon becoming the 4th.
This years “Autumn Moon” or “Harvest Moon” falls on September 18th and 19th in North America, and can be best described as being full very nearly at the same time the moon rises and the sun sets. On the 18th the moon will rise being better than 99% illuminated, but will not be exactly full until around 7:30am EST on the 19th, as the sun is rising to the east and the moon is setting in the west. So, on either the 18th or 19th the moon as it rises or sets will appear Full Phase to the naked eye or with binoculars.
(Stellarium Image facing east-southeast after sunset in rural Union Co., NC)
Often the October full moon claims the Harvest Moon title, since the closest full moon to September 22nd occurs during the first week of Autumn. On average this occurs about every 4 years. The last October Harvest Moon was in 2009.