Shine on, shine on Harvest Moon (9/29)

The Sky This Week, 2012 September 25 – October 2 — Naval Oceanography Portal

Full Moon occurs on the 29th at 11:19 pm Eastern daylight Time. Since this Full Moon occurs closest to the autumnal equinox it is almost universally known to Northern Hemisphere residents as the Harvest Moon. The name derives not only from the season but also from a curious quirk of orbital geometry. For viewers in mid to high northern latitudes the Moon seems to skip along the eastern horizon as it rises from night to night around the time of the full phase. In fact, at latitudes north of the Arctic Circle the Moon rises earlier on successive nights! For most of us, though, the difference in moonrise times is somewhere between 15 and 30 minutes for a few days around Full Moon, depending on latitude. Thus the effect is one where the light of the rising Moon adds to the light of twilight, enabling farmers to squeeze a little extra time into their harvest activities each day. Out of the many different names that sky lore ascribes to the year’s various Full Moons, the Harvest Moon is probably the most widely recognized by the general public, followed by next month’s Hunter’s Moon. Of course, in the Southern Hemisphere the opposite case applies; their "Harvest Moon" would fall near the vernal equinox in March.

The Sky This Week, 2012 September 25 – October 2 — Naval Oceanography Portal