harvest_moonThe Harvest Moon is the full Moon that occurs closest to the autumn equinox. In most years that occurs in September, but in some years – like this year – it occurs in October.

It is said that at the peak of harvest, farmers can work late into the night by the light of this full moon. That’s not all legend and tradition. Usually the full Moon rises an average of 50 minutes later each night, but for the few nights around the Harvest Moon, the Moon seems to rise at nearly the same time each night – just 25 to 30 minutes later across the U.S., and only 10 to 20 minutes later for much of Canada and Europe.

Since many of our American moon traditions come from the Native Americans, I usually look to their traditions when writing about full moons on this blog each month. Their diet staples were corn, pumpkins, squash, beans, and wild rice and all of them would typically be ready by this full moon (though, obviously, this varied by tribe and location).

The Harvest Moon was the only full moon given the same name by both the English and by the Native Americans of eastern and northern North America.

The Harvest moon is often confused with the Hunter’s Moon which is a more modern nickname for the moon that is the first full moon after the Harvest Moon. (That will be November 2 this year.)

I asked a few friends what they thought the “harvest moon” meant. The most common answer was that it was “that orange moon in fall.”  Well, the Harvest Moon seems to be bigger or brighter or more colorful than other moons. These effects have to do with the seasonal tilt of the earth.

The warm color of the moon shortly after it rises is an optical illusion, based on the fact that when the moon is low in the sky, you are looking at it through a greater amount of atmospheric particles (including pollution) than when the moon is overhead. The atmosphere scatters the bluish component of  but allows the reddish component of the light to travel a straighter path to your eyes. All celestial bodies look reddish when they are low in the sky.

(Lots of illusions out there – that blue moonlight is really reflected white light from the sun.)

And why does it look bigger? The human eye perceives a low-hanging moon to be larger than one that’s high in the sky. This is known as a Moon Illusion and it can be seen with any full moon. (It is also true of constellations viewed low in the sky.)

Did you know that the full moons of September, October and November as seen from the northern hemisphere correspond to the full moons of March, April and May as seen from the southern hemisphere?