The full moon of September, called the Harvest Moon, will grace the skies Sept. 24, just two days after the autumn equinox.
The moon becomes officially full on Sept. 24 at 10:52 p.m. EDT (0252 GMT on Sept. 25), according to NASA's SkyCal. For New York City observers, the nearly full moon will rise on that day at 7:01 p.m. and set the next morning at 7:03 a.m., according to the U.S. Naval Observatory (USNO).
On the opposite side of the sky, Venus will be just visible over the horizon, as the planet is getting closer to the sun from Earth's vantage point. Venus will be hard to spot, though. At sunset, the planet will be only about 9 degrees above the horizon, and the planet will set at 7:43 p.m. in New York, according to calculations from heavens-above.com. As bright as Venus is, the sky won't be dark enough to see the planet until just before it sets, so a flat horizon and a keen eye will be necessary.
Mercury will be just emerging from superior conjunction (which will be on Sept. 20). That's the point where the planet is behind the sun from the point of view on Earth. Mercury will be basically invisible; even though at sunset it will be east of the sun and will slowly make its way into the evening sky, it will be only a degree and a half above the horizon at sunset.
(It is important to note that the inner planets' proximity to the sun makes looking for them a bit dangerous. Never point binoculars or a camera lens at the sun without proper filters, and wait until the sun sets before trying to track the planets.)
New York City area observers will see Mars rise at 4:37 p.m. on Sept. 24 and will set at 1:40 a.m. the next morning, so when the full moon rises, it will be about 20 degrees above the eastern horizon, in the constellation Capricornus. Capricornus is a relatively faint constellation, so Mars will stand out because of its brightness and distinct reddish color. As observers turn their gaze westward, they will see Saturn, which by 7 p.m. will have just passed the meridian, the highest point in the sky it will reach. Saturn will be about 26 degrees up and nearly due south, in the constellation Sagittarius.
Jupiter will be in the western half of the sky, about as high as Mars is after sunset, but in the opposite direction. So, both planets will "frame" Saturn. The planet will set at 10:38 p.m. local time in New York City. Sagittarius will be a bit brighter than Libra or Capricornus, and Saturn can be spotted by looking for the steadier light in Sagittarius' "teapot" shape; generally, stars twinkle, but planets do not.
The full moon tends to overwhelm the fainter stars. But in the late-September sky, there are still constellations that can be seen despite the brightness of both the moon and city lights. For example, as the moon gets higher, the brighter winter constellations, such as Taurus and Orion, will appear in the eastern sky; by midnight, those two will have risen in the east and cleared most buildings.
The September full moon is often called the Harvest Moon, according to the Old Farmer's Almanac, because that was when the corn harvests traditionally started. Sometimes, such as in 2017, the September moon is further away from the autumn equinox than the October full moon is, and in those situations, it is called the Corn Moon. This year, though, the September full moon is closer to the equinox.
Besides being a marker for North American harvests, the full moon of September marks the Jewish holiday of Sukkoth, also called the Feast of Tabernacles. Observant Jews will construct a sukkah, a small structure with a roof of natural material, in order to spend time inside and commemorate the time in the wilderness after the exodus from Egypt described in the Torah.
The Ojibwe, who live near the Great Lakes, referred to the ninth moon of the year as the Falling Leaves Moon. The Cree of Ontario called the September full moon the Rutting Moon because it was when many animals started mating (notably, deer). In the Pacific Northwest, the Haida called it the Cedar Bark Moon (Kíit'aas Kungáay), according to the Tlingit Moon and Tide Teaching Resource published by the University of Alaska in Fairbanks.
In China, the eighth lunar month (which, in 2018, is September; it shifts year to year) is called Guìyuè, or Osmanthus Month, for when the eponymous flowers bloom, and the full moon occurs on the 15th day, halfway through. The day of the full moon in the eighth month is called Mid-Autumn Day and is an important festival in China, according to travelchinaguide.com.
In the Southern Hemisphere, September marks the beginning of springtime, with the days getting warmer and longer. The Māori of New Zealand called the lunar months of August and September "Mahuru," meaning "The Earth has now acquired warmth, as well as vegetation and trees," according to the Encyclopedia of New Zealand.