The full moon gets some company from our solar system's planets this month.
The name of the full moon closest to the autumnal equinox, "Harvest Moon," reflects that September was the beginning of the harvest season in the Northern Hemisphere, especially in Europe.
September's full moon will be bracketed by close approaches to Saturn on Sept. 8 and Jupiter on Sept. 11. In New York City, the moon will be situated in Aquarius, rising the evening of Sept. 10 at 7:45 p.m. (opens in new tab) The moment when it is officially full occurs just before moonset in the morning, which occurs at 6:29 a.m. local time. The moon sets the next morning at 7:42 a.m.
Related: The brightest planets in September's night sky: How to see them (and when)
A full moon occurs when the moon is on the opposite side of the Earth from the sun. Technically, its celestial longitude is 180 degrees away from the sun in the sky. The moon's orbit is tilted about five degrees from the plane of the Earth's orbit, so even though the moon is "behind" the Earth, it isn't in the Earth's shadow each time it makes a circuit of our planet. On the occasions when it does pass through the shadow of the Earth we see a lunar eclipse, but that won't happen this time (the next eclipse is due on the night of Nov. 7-8).
If you're looking for binoculars or a telescope to see the full moon, our guides for the best binoculars and the best telescopes have options that can help. If you need photography gear, consider our best cameras for astrophotography and best lenses for astrophotography to prepare for the next planet sight.
The moon's conjunction with Saturn
On Sept. 8, the moon will make a close pass to Saturn when it is in conjunction with the planet, at 6:31 a.m. Eastern Daylight Time (opens in new tab). The moon sets in New York City by 3:56 a.m. EDT so the conjunction itself isn't visible, but the moon rises at 6:12 p.m. on the evening of Sept. 7, and Saturn rises at 6:17 p.m. The two will be within about 4 degrees of each other, and by about 8 p.m. both will be about 20 degrees above the southeastern horizon. Saturn will be to the left of the moon (from the point of view of Northern Hemisphere observers).
The conjunction itself will be visible in the Pacific time zone and points west, where it happens before the moon sets. For example, in San Francisco the moon sets at 4:28 a.m., about an hour after the conjunction at 3:31 a.m. local time. The moon will be low in the southwest, about 8 degrees high, with Saturn above it and to the right. From Honolulu, the conjunction will occur at 12:31 a.m. local time on Sept. 8, and as Hawaii is further south the moon and Saturn will be higher in the sky – the moon will be 41 degrees high in the south, and Saturn will be 45 degrees high.
In the Southern Hemisphere, the conjunction will be visible in New Zealand and Australia in the evening on Sept. 8. Kiwis will see the conjunction at 10:31 p.m. local time, with the moon and Saturn 65 and 62 degrees high to the north, with the moon appearing to pass directly above the ringed planet. Residents of Sydney, Australia will see the conjunction two hours earlier, at 8:31 p.m., when the pair will be similarly high but more towards the northeast.
A close pass by Jupiter
On Sept. 11 our satellite makes a pass by Jupiter, though in this case for people in the Americas and western Europe it will happen during the day, at 11:16 a.m. Eastern Time (opens in new tab). However the moon will still be close to the planet when it rises in New York at 8:09 p.m. Eastern Time. By 9:30 p.m. one will see Jupiter (which rises at 7:50 p.m. (opens in new tab)) to the right of the moon, which will be low in the east.
This conjunction will be visible if one is in New Delhi or points east, where the moon will pass within less than two degrees (opens in new tab) of Jupiter at 8:46 p.m. local time; moonrise is at 7:23 p.m. The moon will be just below and to the right of Jupiter, and about 17 degrees above the horizon in the east. Moving eastwards the conjunction happens later, so that the pair are higher in the sky – in Bangkok it occurs at 10:16 p.m. local time when Jupiter and the moon are 42 degrees above the eastern horizon.
Observing the full moon is quite easy even with small binoculars or a telescope, but it is sometimes difficult to make out fine details on the surface because it is so bright, and the lack of shadows reduces the contrast. A full moon means that the sun is directly overhead from the point of view of someone standing on the moon so waiting until a day or two after the full moon or observing one or two days before the full moon is sometimes better.
That said, binoculars or a small telescope will show some details of the maria, the dark patches on the face of the moon that create the "man in the moon" image. That figure is from European legends which said he was a man banished to the moon (opens in new tab) for gathering sticks on the Sabbath. While Europeans tended to see a human face, East Asian and many Native American traditions call the figure a rabbit.
Other planets
On the night of the full moon itself, other planets don't become visible until much later on Sept. 10. Mars, for example, rises at 10:56 p.m. in New York City (opens in new tab) (its rising time will be similar in other cities in mid-northern latitudes). In the constellation Taurus, it will make a pair with Aldebaran to the right – both are similarly colored, with Mars having the more striking reddish hue.
Venus, meanwhile, is getting lost in the glare of the dawn sky; in New York the planet rises at 5:36 a.m. on Sept. 11 (opens in new tab), while the sun comes up at 6:32 a.m. Eastern Time. (opens in new tab) That means that even bright as it is, the planet will be difficult to catch.
Mercury is lost in the sun's glare; it rises during the day (at 8:26 a.m. Eastern) and sets at 7:40 pm., only 30 minutes after sunset.
September's constellations
The constellations visible in September are still largely those of summer; early in the evening, about 8 p.m., the Summer Triangle is still visible near the zenith. Scorpio and Sagittarius will be in the south. As the night of Sept. 10 progresses one will see the summer stars set and the fall stars rise; by midnight Pegasus and Andromeda will both be high above the eastern horizon. Pegasus is recognizable by the "Great Square" which is an asterism that marks the legendary winged horse's wings and the head of andromeda (which will be the star on the right-side corner).
September's full moon around the world
Looking for a telescope to see the planets or next skywatching event? We recommend the Celestron Astro Fi 102 (opens in new tab) as the top pick in our best beginner's telescope guide.
Native people in North America had a number of different associations and names for the September lunation and full moon. According to the Ontario Native Literacy project, the Cree peoples called it the Rutting Moon, because elk in September start to rub the velvet off of their antlers ahead of the mating season, while the Ojibwe called it the Falling Leaves Moon. The Cherokee called it the Nut Moon, for when many trees start bearing them. In the Pacific Northwest the Tlingit called the lunation of September the Young Animals Moon, while the Haida called the month "Cedar Bark for Hats and Baskets."
In the southern hemisphere September is in the spring, with the days getting warmer. For the Māori the lunar month begins at the new moon, so a full moon is about the halfway point of the August-September lunation, and they called it Mahuru: "The Earth has now acquired warmth, as well as vegetation and trees," according to the Encyclopedia of New Zealand.
Editor's note: If you have an amazing full moon photo you'd like to share for a possible story or image gallery, you can send images and comments to spacephotos@space.com.
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