September is Saturn’s time to shine. We also check on Comet Nishimura — now at 5th magnitude and still brightening — and look forward to a dramatic asteroid occultation. Not to mention that Jupiter just took another hit.

Saturn montage 2018-2023
Australian amateur astronomer Niall MacNeill created this six-year montage of Saturn's closing rings with images taken through his 14-inch Celestron EdgeHD. Careful examination reveals subtle variations in the planets cloud belts and zones. The inclination of the rings has narrowed from a maximum of 27° in 2018 to the current 9.3°. They'll be edgewise in March 2025.
Niall MacNeill

Saturn's return to the evening sky is always one of the year's most anticipated sights. Most newcomers are surprised at their first look. How many times at a public star party have you heard someone say the planet looks fake? You can't really blame them. The ringed planet has no ready analog in the everyday world. What's this — a ball surrounded by a levitating ring? Looking through my telescope one night, someone remarked that the planet looked like an emoji, which made me laugh because they were dead-on. Saturn is alienness perfected. Its unique appearance makes it a guaranteed "wow" getter.

Saturn 2023 opposition
At opposition last month the faster Earth temporarily lined up on the same side of the Sun as Saturn. The two planets were then at their closest for the year. The rings have since opened up to 9.3°. Not to scale.
Bob King with Saturn image by Christopher Go

The ringed planet reached opposition on August 27th, shining at magnitude +0.4 with a disk 19″ across and rings extending their girth to 44″. Saturn is nearly as big and bright this month with the advantage of being higher up in the sky at nightfall. Many amateurs have commented on the narrow, edgy tilt of the rings this apparition compared to last year when they were fanned out at nearly 14°. While closing rings make it easier to see dimmer moons close to the planet (due to less scattered light), spotting Cassini's Division, the apparent 4,800-kilometer-wide gap between the A and B rings, has become a challenge. So far this summer I've seen it flicker into view in my 10-inch Dob on just a few occasions.

Saturn in Aquarius 2023
You'll find Saturn slowly moving westward in retrograde motion in the dim constellation Aquarius this month not far from two well-known asterisms — the Water Jar of Aquarius and the Great Square of Pegasus.
Bob King

For the same reason the innermost C ring may require concentration and good conditions to discern. Look for a filmy, gray glow interior to the B ring contrasting with the dark gap just above the planet's disk. You might also glimpse its presence as a fuzzy gray stripe bordering the northern edge of the shadow cast by the rings on the planet's cloud tops. Around opposition Saturn's shadow remains well hidden behind the planet's globe. Keep watch! It will return in the coming weeks as it pivots eastward and nibbles its way into the rings where they pass behind the planet. The shadow's return enhances Saturn's 3D appearance.

Saturn features guide
This portrait of Saturn from August 22, 2023, reveals many features in the globe-and-ring system worthy of study. A 6-inch or 8-inch telescope will show Cassini's Division, but you'll need a 12-inch or larger telescope to discern the much narrower Encke Gap, which is swept free of ring debris by the moon Pan's gravity. Note the difference in color between the hemispheres. North is up.
Damian Peach

The North Equatorial Belt is still the planet's most prominent atmospheric feature in a small telescope. In 8-inch and larger instruments additional temperate belts and the gray cap of the North Polar Region appear in excellent seeing. With the closing of the rings, Saturn's southern hemisphere finally peeks back into view. Try spotting the South Equatorial Belt located immediately south of the ring plane. Planetary imager Christopher Go recorded an unusual disturbance there in images taken in late August.

Saturn SEB disturbance
Ruffled clouds that may indicate a disturbance in Saturn's South Equatorial Belt (SEB) appear on August 26, 2023. The feature was located at System I longitude 68°, II = 296°, III = 252°. The moon Dione is seen below Saturn.
Christopher Go

Saturn has generally lagged behind Jupiter in its total number of known moons. But with a flurry of recent new discoveries its tally now stands at 146 compared to Jove's 95. Five Saturnian moons are typically visible in a 6-inch scope — Titan (magnitude 8.4), Rhea (9.8), Tethys (10.3), Dione (10.5), and Iapetus. The last has a split personality with one hemisphere covered in bright, reflective ice and the other in dark, organic compounds. Because it's tidally locked to Saturn (in a 79-day orbit), we always see the bright side at western elongation — when Iapetus is an easy catch at magnitude 10.2 — and the dark side at eastern elongation — when it dims to 11.9. Larger telescopes at high magnification will show Enceladus (11.8), distant Hyperion (14.3), and Mimas (13.0), which orbits so close to the planet it's difficult to pull from the glare.

Saturn and moons Sept. 6
Saturn gains a temporary extra "moon" on September 6th when 9th-magnitude HD 211990 joins the lineup. Planet and moon positions are shown for 10 p.m. CDT. North is up.

On September 9th Iapetus reaches western elongation and shines at peak brightness. It reaches the other end of its orbit (eastern elongation) on October 18th and finally completes the cycle on November 27th when it once again stands at western elongation. You can use Sky & Telescope's Saturn moons finder to locate the planet's five brightest satellites any time of night you like. A phone app like Sky Safari or the free desktop planetarium program Stellarium will show the location of all moons visible with the largest amateur telescopes.

Comet Nishimura's spectacular tail

Comet Nishimura Sept. 2, 2023
Gerald Rhemann photographed Comet Nishimura's stunning gas tail on September 2, 2023, under exceptionally clear skies. He used a Moravian C3 61000 camera with an ASA H8“ f/2.9 hyperbolic astrograph. The final image is a combination of separate 75- and 100-second exposures in L (luminance), red, green, and blue channels.
Gerald Rhemann

Comet Nishimura (C/2023 P1) is still tearing up the dance floor as it approaches its September 17th perihelion. I last observed it on September 5th in last-quarter moonlight. Even in 10×50 binoculars the bright, fuzzy head was easy to spot, trailed by a short, westward-pointing tail visible with averted vision. Through a 15-inch telescope the coma was small (3′) and strongly condensed with a pleasing blue-green color from carbon emission. The tail emerging near the head was bright, straight, and pencil-thin. Farther out it expanded and looked fluffier with a total length of ~45′. I was able to keep the comet in view in both telescope and binoculars until 5:30 a.m. — a half-hour into morning twilight. Its overall magnitude was around 5.5.

Comet Nishimura animation
In this 20-minute animation from September 2nd material streaming from the comet is carried off in braids and kinks by variations in the speed and direction of the solar wind.
Michael Jaeger

Although I'm aware that accomplished astrophotographers can pull off amazing views of objects even under the worst of conditions I was wonderstruck looking at recent photos from Michael Jaeger and Gerald Rhemann. Their work beautifully illustrates the dynamic interaction of the solar wind and the comet's ion tail and reminds me why I like comets so much. You'll find a steady stream of fresh images on the ICQ Comet Observations page on Facebook.

Comet Nishimura September map
This map shows the sky for latitude 40° north at the start of dawn about 90 minutes before sunrise for the contiguous U.S. and Canada. On September 6th Comet Nishimura stands about 10° high but dips lower each morning until it's only a few degrees above the horizon on September 11th. Its gradual decline is offset by the stars rising 4 minutes earlier each morning. More good news — the comet is bright enough to see into early twilight. Venus moves only a little during the time frame, making it — along with Epsilon (ε) Leonis (Algenubi) and Gamma (γ) Leonis (Algieba) — useful celestial guides.
Stellarium with additions by Bob King

In my previous post I included maps for locating Comet Nishimura. While those will still work perfectly well, I wanted to include a more realistic chart showing how the comet appears in a real-life setting. As you can infer from the map an unobstructed horizon is crucial. Interference from a bright Moon will be a bit of a bother until about September 8th. Plan to be out about 2 hours before sunrise to anticipate the comet's appearance. The window of observation before twilight encroachment will be brief — only about 20–25 minutes. Binoculars will help pinpoint its location but do bring a telescope for a closer look. You won't be disappointed.

Comet Nishimura Sept. 5, 2023
Comet Nishimura climbs above the trees into good view just before the start of dawn on September 5th from Duluth, Minnesota. Details: 200-mm lens at f/2.8, ISO 400, 20-second exposure on a tracking mount.
Bob King

Impact at Jupiter!

Watch the latest Jupiter impact captured by Tadao Ohsugi on August 28, 2023.

The biggest planet has just taken another hit. In what appears to be the 12th recorded Jovian impact Japanese amateur astronomers Tsutomu Ishibashi and Satoshi Ota captured the flash at 16:45:57 UT on August 28, 2023, at Jovian latitude 45° north and system II longitude 128°. Another observer visually observed the smash-up on a monitor between photo shoots. In all there have been at least seven independent observations of the event, making it one of the most widely observed impacts. Images taken in methane light 42 minutes after the strike failed to show evidence of a dark impact "scar" like those recorded during several previous Jupiter collisions indicating that whatever it was that struck the planet was very small. Further observations and photos are available at ALPO Japan.

Jupiter impact August 28, 2023
Amateur astronomer Satoshi Ota captured the bright flash of an impact at Jupiter on August 28, 2023.
Satoshi Ota, courtesy of ALPO Japan

If you were imaging Jupiter around the time of impact and recorded the sight please contact Marc Delcroix, Ricardo Hueso, and Isshi Tabe at their respective email addresses:

delcroix.marc at
ricardo.hueso at
isshi7717 at

Interamnia occultation widely visible across U.S.

Interamnia visibility map
Observers within the broad path shown here will see the 329-kilometer-wide asteroid (704) Interamnia occult a 9th-magnitude star in Auriga in the morning hours of September 13th.

When was the last time you witnessed an asteroid occulting a star? On September 13th at around 10:16 UT (6:16 EDT), observers within a broad path from southern California to lower Michigan will see the large 12th-magnitude asteroid (704) Interamnia occult a 9th-magnitude star in Auriga for up to 17 seconds. The target star will fade nearly 3 magnitudes, making for a dramatic sight in telescopes as small as 4 inches. The International Occultation Timing Association (IOTA) is treating the occultation as an opportunity to bring new observers into the fold. There's also a possibility of discovering a small moon orbiting Interamnia by coordinating observations outside the main path. Curious? Find maps and more details at the IOTA observation campaign.


Image of Rod


September 6, 2023 at 3:33 pm

I did place some observations notes here on Saturn viewing 01-Sep and Nishimura comet early this morning, site reported 4.9 magnitude for this morning viewing of the comet. Nothing great in my 10x50 binoculars but distinct small fuzzy.

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Bob King

September 6, 2023 at 7:55 pm

Hi Rod,
Thank you for doing so and feel free to update here as well regarding the comet. I see it's magnitude 5 now. Nice to see it's still holding together. I should be able to see it next on Sept. 8 at dawn. Looking forward to a thinner moon and darker skies.

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Image of SNH


September 7, 2023 at 5:11 pm

Saw it this morning without trouble in 12x60 binoculars as an out-of-focus star. At 5:20am local time (7th at 10:20UTC), it was as bright or slightly brighter than nearby 22 Leonis (mag +5.3). So, I'm calling it +5.2. Seemed to detect a tail, but it was vague. Was able to see +3.0 Epsilon Leonis naked-eye and suspect +3.9 Mu Leonis just above the comet. Again, I'm thinking this one won't get to be naked-eye since it would have to be no lower AND a full magnitude brighter!

Will look to see it again Sat (9th) and Sun (10th) morning.

Scott H.

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Bob King

September 8, 2023 at 10:37 am

Hi Scott,
I'm surprised you didn't see more of a tail in the 12x60s. The comet's brightness appears to be stalling a little, currently at 4.5 or a bit fainter. Were it higher up there would be regular naked-eye sightings. I was so hoping to see it this morning (Sept. 8) but despite the forecast the clouds were stubborn. Still hopeful for tomorrow morning.

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September 12, 2023 at 5:32 pm

I attempted and failed to see the comet on the morning of the 11th. Looks like the last time for me was on the 10th, just one week from perihelion. That morning I estimated it at around magnitude +4.5, but in such bright twilight that it wasn't anything to wake the family up about.

However, at an angular distance of just 18.3 degrees from the Sun and being inside the orbit of Mercury, it was the second closest comet to the Sun I've ever seen! The one that has been holding firmly onto first place in my record book is C/2011 L4 (PanSTARRS), which I first saw in the evening sky while just 16* from the Sun...

Checking COBS, it appears I'm not the only one who had their last sighting of it on the 10th. I wonder if I'll be able to see it in binoculars on its way out of the solar system?


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