As we officially transition to fall with the arrival of the autumnal equinox tonight, we’re going to experience a rare astronomical coincidence of sorts as the Harvest Moon will herald the start of fall. The Harvest Moon is the full moon closest to the autumnal equinox and gets its name because farmers many years ago could rely on the brightness of the moon in the evening and the also during surrounding days, to harvest their crops. An added bonus for those farmers is an oddity of the earth’s ecliptic, or orbit around the sun that keeps the moonrise times in the successive nights around the full moon closer together than usual meaning there would be more evening light after sunset than during other parts of the year. Even though the moon won’t officially be full until 4:17 am tomorrow and the equinox occurs at 10:09 tonight, we can still say they occur on the same day because the equinox is considered to actually occur first at the Prime Meridian at 3:09 Greenwich Mean Time on the 23rd, the same day as the full moon occurs for all of us. Our first look at that full moon in North America will be tomorrow evening when it rises at 6:50 pm. Sadly, our viewing of the Harvest Moon will be limited if not impossible thanks to a large, heavy rain producing storm system that will move in tonight and keep clouds and thundershowers around through tomorrow before finally moving out Friday morning. Keep your fingers crossed and maybe we’ll at least catch a glimpse! Incidentally, the next time the Harvest Moon and autumnal equinox occur on the same day will be in 2029. Happy Autumnal Equinox Day!
Posted under climate
This post was written by tschmidt on September 22, 2010