Night Sky for September 2021

Visible planets and highlights of the September sky

By Bob Berman
September 1, 2021
Field and Stars
Photo by Taylor Durrer on Unsplash

Visible planets, the autumnal equinox, and the Harvest Moon! See highlights of the September night sky from The Old Farmer’s Almanac astronomer Bob Berman.

Bright Planets of September

by Bob Berman, as featured in The 2021 Old Farmer’s Almanac

Oh, what a night! The mild evenings of September are perfect for planet and stargazing. Even better, we find that planets Venus, Jupiter and Saturn are bright and visible in the evening all month long!

At twilight, a nice series of conjunctions happens in the west his month.

  • On the 1st, dazzling Venus is to the upper left of Mercury, with that innermost planet very low but bright at exactly magnitude 0.0. On the 8th, look for Mercury below the thin crescent Moon.
  • On September 9, at dusk, the young Moon will stand to the upper right of Venus. The bright planet appears just about the horizon.

The crescent Moon and Venus. Credit: NASA/Bill Dunford

  • Then, on September 10, after sunset, look again for the crescent Moon; Venus appears to its lower right, very near the bright double star Spica. Mercury will be nearby, low near the horizon, though you may need binoculars to find it.

How the Moon and Venus will appear on September 10, 2021. Credit: NASA/JPL-Caltech

  • On Tuesday, September 14, Neptune reaches opposition. Neptune will be visible all night–so it’s as good as chance as any to spot Neptune. This is the only planet in our solar system that is not visible to the naked eye, so you will need a pair binoculars or small telescope. I’ll write more about Neptune’s opposition later.
  • Mark September 16 and 17 on your calendar. On the 16th, the Moon floats below Saturn, and then appears to hover right below Jupiter on the 17th! See this article from EarthSky to see a great chart and learn more.

See planet rise and set times from your location for the U.S. and Canada.

Full Harvest Moon

September 20 brings the Full Harvest Moon—just two days before the fall equinox. (The full Moon that happens nearest to the autumnal equinox always takes on the name “Harvest Moon.”) Learn more about the Harvest Moon (a true astronomical phenomenon) and why it’s so special!

Autumnal Equinox

September 22 brings transition from summer to fall! Officially, autumn begins at the moment of the equinox—3:21 a.m.on the 22nd. Learn more about the first day of fall in the Northern Hemisphere!

Pegasus Shines in September

This month, watch for Pegasus, the Winged Horse in the southeastern sky! A useful guide to this asterism (unofficial star pattern) is the Great Square, which outlines Pegasus’ body. See our star chart and how to find Pegasus.


The 2021 Old Farmer's Almanac


Reader Comments

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Planets viewed in Palenville, NY evening sky's

Hi Neighbor, I have followed you for many, many years, and being a Greene County old timer, I wish too thank you for years of invaluable information, service to our community, and reading ?entertainment. I live not far from you, in Palenville, NY, the setting of Rip Van Winkles wandering up our cove, too go bowling with the crew of the Halfmoon and sleep. When I walk my best pal, at approximately, every evening before bed, between 10:30PM and 11:00PM, and then again every morning around 5:30-6:00 AM, and as I look at most of the wonderous and fantastical night and pre-dawn sky events, they are always at different compass positions, from your great articles of our beautiful nocturnal heavens. Take Jupiter, last night it was low in the SW sky, not South, and has been there for, pretty much, all summer long. Then in the morning it sits due East/South East, very bright in the dawn rising sun, again all summer long. Mars, has moved around a bit over the last few months, and has brightened and dimmed as it moved in the sky all summer. This morning, September 3rd, 2020, it was very bright, directly above my head, as bright and big as I have ever seen the red planet with my naked eye. And, last night at 11:00PM Mars was in the N/NW Sky, directly over Katterskill Cove notch. Saturn has not been as easy too see with the naked eye, but I have, about a couple/few weeks ago, Jupiter and Saturn were due west fairly high in the evening sky, not far from each other, just under the waxing, or was it waning, I forget, moon for several nights, moving a bit each night's bedtime walk. My view is limited living in a Cove, (bowl, notch, waterway), and surrounded by tall pines, oaks, hemlocks, and maples, making Venus, and Mercury sightings virtually impossible. All that being said, generally my veiw is always slightly skewed from your insightful points of veiw. And, I just have always wondered why? Again Bob, thank you for years of service too, not only the Almanac and local newspapers, but for your work connserving our beautiful home, here in Greene County New York.


This is a very exciting season! I am very much looking forward to all the events Bob has beautifully described. Thank you so much OFA and Bob for this column!