September is called the harvest moon because farmers can continue their harvest late into the night by the light of the full moon. Other names for this moon are the Wine Moon, the Elk Call Moon and the Singing Moon. A low hanging harvest moon can give an array of colors that is not usually seen. There is an added treat to watching a harvest moon; this is called moon illusion because the rising or setting moon looks bigger than when it does high in the sky.
~Swami Muktibodhananda Saraswati, Commentary, 1985 translation, Hatha yoga Pradipika