The New Student's Reference Work/Harvest-Moon
Har′vest-Moon. Although the moon usually rises later by a considerable interval on each successive night, owing to her motion about the earth, yet the further one goes toward the poles, the greater is the variation in the amount of her retardation. Thus in New York the moon nearest to September 22nd, the autumn equinox, varies in rising only some 25 minutes. This is because she is then in that part of her orbit which makes the least angle with the ecliptic. When a full moon occurs at about this date, it is known as the harvest-moon, because it is very convenient in harvesting to have a rather full moon, lasting almost all night, for several nights together.