A full moon captured July 18, 2008.NASA/Sean Smith
A full moon captured July 18, 2008.If you've ever wondered what, exactly, a harvest moon looks like, poke your head outside Saturday. That's when this year's harvest moon will rise.The harvest moon is the full moon closest to the autumnal equinox,which this year was on Sept. 22.It's different from the other full moons because it rises at roughly the same time for several nights running, giving more light."In the days before tractors with headlights, having moonlight to work by was crucial to getting the harvest in quickly before rain caused it to rot," says Alan MacRobert, an editor at Sky &Telescope magazine. The harvest moon will rise this year at 11:19 p.m. ET.On average, the moon rises 50 minutes later each day than it did the day before. However, at this time of year, because of the angle of the moon as it orbits Earth, "the moon is rising at roughly the same time it rose the night before," says Ed Krupp, director of the Griffith Observatory in Los Angeles.So for about three days in a row, the full moon is coming up just after the sun sets. "This brings a great deal of light into the early evening sky, which was important for the people harvesting because it extended the period of useful work time they could work in the fields," Krupp says.The moon may look bigger and seem closer, but it's not, says David DeVorkin, a senior curator at the Air and Space Museum in Washington, D.C. Generally, photos of harvest moons are taken with telephoto lenses, distorting the size. The harvest moon can appear more reddish, though, because of coloration caused by dust in the atmosphere, but it depends on where you are.The change in the time of moonrise "has to do with the angle along which the moon is traveling in its orbit," Krupp says. At the fall equinox, "the angle is very shallow, so it doesn't go so far below the horizon and as a result comes up again at about the same time."The harvest moon isn't the only one to have a name, though few are remembered now. The new moon after the harvest moon was typically called Hunter's moon, because it aided hunters stalking night game as fall deepened. For more information about reprints & permissions, visit our FAQ's. To report corrections and clarifications, contact Standards Editor Brent Jones. For publication consideration in the newspaper, send comments to email@example.com. Include name, phone number, city and state for verification. To view our corrections, go to corrections.usatoday.com.