Comet Chasing in September

Comet chasing is the visual observation of telescopic comets.  Jump to:  Observing synopses    Summary data


News

There are two comets visible in binoculars this month, two comets visible in small telescopes, and two comets visible in a 6-inch (15cm)  telescope this month. Many more are visible in larger instruments. The Observing Synopses will tell which comets are visible to you. 

  • New Comet Discovery C/2023 P1 (Nishimura) was discovered by H. Nishimura in images taken on Aug. 11 UT, at Gomyo, Kakegawa, Japan with a digital camera.This new 10th magnitude comet is low in the eastern sky before dawn. It has been observed visually, and is said to be relatively easy to spot, even though it is low on the horizon. Interested in how this new comet discovery is being followed up? See our new comet follow up video  

  • 2P/Encke is set to reach its perihelion on October 22, peaking at a brightness of magnitude 3.7 by late October. With a 3.3-year orbit, Encke boasts the shortest orbital period of any known comet in our solar system.

  • Comet 12P/Pons-Brooks, a well-documented comet perhaps observed as early as the year 245, recently experienced an unexpected outburst, catapulting from a magnitude of 16.6 to 11.6 in a single day. This sudden activity was first noted on July 20, 2023. The comet has since displayed an unusual coma shape, characterized by a distinctive 'notch' in the anti-sunward direction. Observations as of August 1, 2023, show the expansion of this irregular coma and a fading of the previously stellar-like pseudo nucleus. Integrated magnitude estimates remain steady for now, although it's anticipated they may begin to fade soon. As it continues its journey towards perihelion on April 21, 2024, this Halley-like comet will be worth keeping an eye on. Here is a link to a video with an animation of the outburst aftermath 

  • C/2021 T4 (Lemmon) passed perihelion in late July, when it also passed within 0.6 AU of the earth.

  • C/2023 E1 (ATLAS) was discovered by the ATLAS survey on March 1. This comet passed perihelion, or closest point to the sun, in early July. It also approached relatively close to earth, at a distance of 0.4 Astronomical Units (AU), on July 1, at magnitude 10. 

  • C/2020 V2 (ZTF) passed perihelion in early May 2023. It is predicted to reach maximum brightness of magnitude 10 in early September.

  • C/2023 A3 (Tsuchinshan-ATLAS) is a discovery made independently by Purple Mountain Observatory (China) and the ATLAS survey (South Africa) that has the potential to be a bright naked eye comet. It will reach perihelion on September 28, 2024, when it will be within 0.5 AU of the earth and 0.4 AU from the sun.. It is predicted to reach maximum brightness in early October 2024. On October 12, 2024 this comet will be moving quickly across the sky at a peak rate of 14 "/min.

  • C/2020 K1 (PANSTARRS) passed perihelion in early May.

  • 237P/LINEAR passed perihelion in mid May and reached maximum brightness in early July.

  • C/2017 K2 (PANSTARRS) passed perihelion in mid December 2022 and is fading.

  • C/2021 T4 (ATLAS) C/2019 T4 (ATLAS) is past perihelion, which occurred in early June 2022, and is fading.

  • 96P/Machholz is a sun grazing comet with an orbital period of 5.3 years. It passed close to the sun on January 30, when it was best observed via solar monitoring satellites such as SOHO. 

  • C/2022 A2 (PANSTARRS) passed perihelion in mid February.  

  • 81P/Wild passed perihelion in mid December and is fading. 

  • C/2019 L3 (ATLAS) is well past perihelion, which occurred in early January 2022. 

  • 73P/Schwassmann-Wachmann passed perihelion on August 25. This comet has a long history of fragmentation, and some very faint fragments have been identified. 

  • C/2022 P1 (NEOWISE) passed perihelion in late November. It was reported to have brightned in late August and is currently predicted to reach maximum brightness of magnitude 13.3 in early November. It appears to be a periodic comet with a period of 94 years, leading to a previous perihelion in approximately 1928.

  • 29P/Schwassmann-Wachmann has frequent outbursts, typically resulting in a brightening of 0.5 - 1.0 magnitudes, which occur roughly every 59 days, typically taking 5-10 days to subside. Up to three subsequent outbursts may occur 5-10 days afterward, each typically smaller than the last, although on some occasions they can be even brighter than the first. These outbursts make 29P one of the most interesting comets to follow, both visually and scientifically. 29P/Schwassmann-Wachmann has a 14.8-year orbital period, and last passed perihelion in early March 2019. It varies in its distance from the Sun from 5.8 AU (at perihelion) to 6.3 AU (at aphelion), which is an unusually small variation for a comet, and remains quite far from the sun at all times. This means that it can be observed more or less continuously.

  • C/2014 UN271 (Bernardinelli-Bernstein) is an interesting Oort cloud comet that was reported as a result of the Dark Energy Survey. Soon after it was made public, images showed a cometary coma. Discovery credit goes to Pedro Bernardinelli and Gary Bernstein. This is a remarkable comet that was at 29 AU in 2014, with a perihelion of 10.9 AU in 2031. Its orbit extends out to 40,000 AU! It was unusually bright for its distance. Recent HST obsrvations that isolate the nucleus estimate the diamter to be between 120 and 140 km, making this possibly the largest comet nucleus yet measured. Because of its distant perihelion, this comet is not expected to become bright enough to be visually observed except in large instruments, and not until the end of the decade, but it is likely going to be the subject of intense scientific scrutiny. 

Comets that have apparently disentegrated: CC/2022 S3 (PANSTARRS), C/2021 P4 (ATLAS), C/2020 Q1 (Borisov), C/2020 P1 (NEOWISE), and C/2019 Y4 (ATLAS). Beware that various other sources often fail to keep track of whether or not a comet still exists!

Comet Visibility in the Eyepiece

This page uses code developed for SkyTools to predict the visibility of a comet in the eyepiece.  Predicting how much aperture is required to see a comet is a very complex task.  Have a look for yourself: a comparison of the predictions below (such as "visible in small telescopes") to the magnitude of each comet shows just how poor an indicator the magnitude alone really is. When you read below that a particular aperture is required to see a comet you can have a reasonable degree of confidence that the comet can in fact be seen in the eyepiece. But always remember, comets are like cats. They both have tails and do what they want, and not always what we expect. This is one of the things that makes comet chasing interesting!

Observing Synopses for September

Explanation of Comet Synopses and charts (read this if you have questions)

2P/Encke: A morning comet visible in binoculars
This comet begins the month in Auriga at magnitude 11.4. Look for a 3' coma. It should brighten rapidly, moving into Leo by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Fairly high in moonlight at ~03:10 Fairly high at ~03:30 Fairly high in the eastern sky during morning twilight at ~03:50 Fairly high in the eastern sky during morning twilight at ~04:20 1-
40o N Not visible High in moonlight at ~04:00 Fairly high at ~04:10 Fairly high in the eastern sky during morning twilight at ~04:20 Fairly high in the eastern sky during morning twilight at ~04:40 1-
Equator Not visible Fairly high in moonlight at ~04:40 Fairly high in the eastern sky at ~04:40 Fairly high in the eastern sky during morning twilight at ~04:40 Low in the eastern sky during morning twilight at ~04:50 1-
30o S Not visible Not visible Not visible Not visible Not visible 1-29

C/2023 P1 (Nishimura): A morning comet visible in binoculars
This comet begins the month in Cancer at magnitude 6.6. Look for a 5.5' coma.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Low in the eastern sky during morning twilight at ~03:30 Very low in the eastern sky during morning twilight at ~03:50 Very low in the western sky during evening twilight at ~19:00 Not visible Not visible 1-18
40o N Low in the eastern sky during morning twilight at ~04:20 Very low in the eastern sky during morning twilight at ~04:30 Not visible Not visible Not visible 1-11, 13-20
Equator Low in the eastern sky during morning twilight at ~05:00 Not visible Not visible Not visible Not visible 1-8, 16-23, 25-25
30o S Not visible Not visible Not visible Not visible Not visible 1-2, 19-28

C/2020 V2 (ZTF): A morning comet visible in small telescopes
This comet begins the month in Cetus at magnitude 9.9. Look for a 4.5' coma. It should fade slowly, moving into Sculptor by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high in the southern sky during morning twilight at ~03:10 Low in the southern sky in moonlight at ~03:00 Low in the southern sky at ~02:30 Not visible Not visible 1-27
40o N Fairly high during morning twilight at ~04:00 Fairly high in moonlight at ~03:10 Fairly high in the southern sky at ~02:30 Fairly high in the southern sky at ~01:40 Low in the southern sky in moonlight at ~01:00 1-
Equator High during morning twilight at ~04:50 High at ~03:00 High at ~02:30 High at ~01:40 Fairly high in moonlight at ~03:50 1-
30o S High during morning twilight at ~05:00 High at ~03:10 High at ~02:30 High at ~02:10 Fairly high in the eastern sky at ~19:50 1-

103P/Hartley: A morning comet visible in small telescopes
This comet begins the month in Perseus at magnitude 11.2. Look for a 3' coma. It should brighten by about 1.3 magnitudes, moving into Auriga by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high in the eastern sky during evening twilight at ~20:50 High in moonlight at ~03:00 High at ~03:20 High at ~03:40 High during morning twilight at ~04:10 1-
40o N Not visible High in moonlight at ~03:50 High at ~04:00 High at ~04:10 High during morning twilight at ~04:30 1-
Equator Not visible High in moonlight at ~04:30 High at ~04:30 High at ~04:30 High during morning twilight at ~04:40 1-
30o S Not visible Low in the northern sky at ~04:40 Low in the northern sky at ~04:30 Fairly high in the northern sky at ~04:30 Fairly high in the northern sky during morning twilight at ~04:30 1-

C/2021 T4 (Lemmon): An evening comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Libra at magnitude 10.9. Look for a 2.5' coma. It should fade by about 1.3 magnitudes by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Low in the western sky during evening twilight at ~19:50 Not visible Not visible Not visible Not visible 1-17
Equator High at ~19:10 Fairly high at ~19:10 Fairly high in the western sky during evening twilight at ~19:10 Fairly high in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~19:00 1-
30o S High at ~19:10 Fairly high at ~19:10 Fairly high at ~19:10 Fairly high in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~19:20 1-

12P/Pons-Brooks: An evening comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Draco at magnitude 11.6. Look for a 1.5' coma. It should brighten by about 0.5 magnitudes, moving into Hercules by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N High during evening twilight at ~20:50 High at ~21:00 High at ~20:30 High at ~20:20 High during evening twilight at ~19:20 1-
40o N High at ~20:10 High at ~20:00 High at ~19:50 Fairly high at ~22:10 High during evening twilight at ~19:00 1-
Equator Fairly high at ~19:20 Fairly high at ~19:20 Fairly high at ~19:10 Fairly high in moonlight at ~19:10 Fairly high at ~19:00 1-
30o S Not visible Not visible Not visible Not visible Not visible 1-24

C/2021 S3 (PANSTARRS): A southern hemisphere morning comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Pyxis at magnitude 12.6. Look for a 50" coma. It should brighten by about 0.6 magnitudes, moving into Antlia by month's end. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Not visible Not visible Not visible Not visible Not visible  
Equator Not visible Low in the eastern sky during morning twilight at ~04:50 Low in the eastern sky during morning twilight at ~04:50 Low in the eastern sky during morning twilight at ~04:50 Low in the eastern sky during morning twilight at ~04:50 1-
30o S Fairly high in the eastern sky during morning twilight at ~05:00 Fairly high in the eastern sky during morning twilight at ~04:50 Fairly high in the eastern sky during morning twilight at ~04:40 Fairly high in the eastern sky during morning twilight at ~04:30 Fairly high in the eastern sky during morning twilight at ~04:30 1-

237P/LINEAR: An evening comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Aquila at magnitude 13.0. Look for a 50" coma. It should fade by about 0.6 magnitudes by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high during evening twilight at ~20:50 Fairly high at ~20:50 Fairly high at ~20:30 Fairly high at ~20:30 Fairly high during evening twilight at ~19:20 1-
40o N High at ~20:10 High at ~20:20 High at ~20:00 Fairly high at ~22:30 High during evening twilight at ~19:00 1-
Equator High at ~20:30 High at ~20:20 High at ~20:00 Fairly high in moonlight at ~23:10 High at ~19:10 1-
30o S High at ~20:40 High at ~20:20 High at ~20:00 High in moonlight at ~19:20 High at ~19:30 1-

C/2023 E1 (ATLAS): An evening comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Pegasus at magnitude 10.9. Look for a 4.5' coma. It should fade rapidly, moving into Aquarius by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high during evening twilight at ~20:40 Fairly high at ~22:50 Not visible Not visible Not visible 1-20
40o N Fairly high at ~20:20 High at ~22:50 Fairly high at ~22:30 Not visible Not visible 1-23
Equator High at ~20:30 High at ~22:50 High at ~22:30 Not visible Not visible 1-24
30o S High at ~20:50 High at ~22:50 High at ~22:30 Not visible Not visible 1-23

C/2022 A2 (PANSTARRS): A morning comet visible in a 14-inch (36 cm) telescope
This comet begins the month in Pegasus at magnitude 12.8. Look for a 1.5' coma. It should fade by about 0.7 magnitudes, moving into Pisces by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high in the eastern sky during evening twilight at ~20:40 High at ~00:10 High at ~23:40 High at ~23:00 Fairly high in the eastern sky during evening twilight at ~19:20 1-
40o N Fairly high in the eastern sky at ~20:20 High at ~00:20 High at ~23:40 High at ~23:10 Fairly high during evening twilight at ~19:00 1-27, 29-
Equator Fairly high in the eastern sky at ~20:40 High at ~00:20 High at ~23:40 High at ~00:50 High at ~19:10 1-26, 29-
30o S Low in the eastern sky at ~21:10 High at ~00:20 High at ~23:40 Fairly high at ~01:50 Fairly high at ~19:40 1-26, 29-

29P/Schwassmann-Wachmann: A morning comet visible in a 16-inch (41 cm) telescope
This comet begins the month in Cancer at magnitude 13.1. Look for a 1' coma. It should brighten slowly.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Low in the eastern sky during morning twilight at ~03:10 Fairly high in the eastern sky during morning twilight at ~03:20 Fairly high in the eastern sky during morning twilight at ~03:30 Fairly high during morning twilight at ~03:50 Fairly high during morning twilight at ~04:10 1-
40o N Fairly high in the eastern sky during morning twilight at ~04:00 Fairly high in the eastern sky during morning twilight at ~04:00 Fairly high at ~04:10 Fairly high at ~04:20 High during morning twilight at ~04:30 1-
Equator Low in the eastern sky during morning twilight at ~04:50 Fairly high in the eastern sky during morning twilight at ~04:50 Fairly high in the eastern sky at ~04:40 Fairly high at ~04:40 Fairly high during morning twilight at ~04:40 1-
30o S Not visible Not visible Low in the eastern sky during morning twilight at ~04:40 Low in the eastern sky during morning twilight at ~04:30 Low in the eastern sky during morning twilight at ~04:30 9-

C/2017 K2 (PANSTARRS): A morning comet visible in very large telescopes
This comet begins the month in Monoceros at magnitude 13.0. Look for a 1.5' coma. It should fade slowly.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Low in the eastern sky during morning twilight at ~03:40 Low in the southern sky during morning twilight at ~03:50 Fairly high in the southern sky during morning twilight at ~04:10 11-
40o N Low in the eastern sky during morning twilight at ~04:10 Fairly high in the eastern sky during morning twilight at ~04:10 Fairly high in the eastern sky during morning twilight at ~04:10 Fairly high at ~04:20 Fairly high during morning twilight at ~04:30 1-
Equator High during morning twilight at ~04:50 High in moonlight at ~04:40 High at ~04:40 High at ~04:40 High during morning twilight at ~04:40 1-
30o S High during morning twilight at ~05:00 High in moonlight at ~04:40 High at ~04:30 High at ~04:20 High during morning twilight at ~04:30 1-

C/2020 K1 (PANSTARRS): A southern hemisphere evening comet visible in very large telescopes
This comet begins the month in Musca at magnitude 13.5. Look for a 1' coma. It should fade slowly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Not visible Not visible Not visible Not visible Not visible  
Equator Not visible Not visible Not visible Not visible Not visible  
30o S Fairly high in the southern sky at ~19:10 Fairly high in the southern sky at ~19:10 Fairly high in the southern sky at ~19:20 Fairly high in the southern sky at ~04:20 Fairly high in the southern sky at ~19:20 1-

C/2019 L3 (ATLAS): A southern hemisphere morning comet visible in very large telescopes
This comet begins the month in Antlia at magnitude 13.7. Look for a 50" coma. It should fade slowly. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Not visible Not visible Not visible Not visible Not visible  
Equator Not visible Not visible Not visible Not visible Not visible  
30o S Not visible Low in the eastern sky during morning twilight at ~04:50 Low in the eastern sky during morning twilight at ~04:40 Low in the eastern sky during morning twilight at ~04:30 Not visible 8-12, 15-28

C/2019 T4 (ATLAS): An evening comet visible in very large telescopes
This comet begins the month in Serpens Caput at magnitude 14.4. Look for a 55" coma. It should fade slowly.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high during evening twilight at ~20:50 Fairly high in the western sky during evening twilight at ~20:40 Fairly high in the western sky during evening twilight at ~20:20 Fairly high in the western sky during evening twilight at ~20:00 Fairly high in the western sky during evening twilight at ~19:30 1-
40o N High at ~20:10 Fairly high at ~19:50 Fairly high at ~19:40 Fairly high during evening twilight at ~19:30 Fairly high during evening twilight at ~19:00 1-
Equator High at ~19:20 High at ~19:10 Fairly high at ~19:10 Fairly high during evening twilight at ~19:00 Fairly high at ~19:00 1-
30o S Fairly high at ~19:10 Fairly high in the western sky during evening twilight at ~19:10 Fairly high in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~19:10 1-24, 30-

C/2022 E3 (ZTF): A southern hemisphere morning comet visible in very large telescopes
This comet begins the month in Columba at magnitude 14.3. Look for a 2.5' coma. It should fade slowly, moving into Puppis by month's end. The best visibility is mid-month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Not visible Not visible Not visible Not visible Not visible  
Equator Not visible Fairly high in moonlight at ~04:40 Fairly high at ~04:40 Fairly high at ~04:40 Not visible 5-27
30o S Not visible High in moonlight at ~04:40 High at ~04:30 High at ~04:20 Not visible 3-27

126P/IRAS: A morning comet visible in very large telescopes
This comet begins the month in Perseus at magnitude 14.4. Look for a 40" coma. It should fade by about 0.6 magnitudes, moving into Cassiopeia by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high in the eastern sky during evening twilight at ~20:50 High in moonlight at ~02:40 High at ~02:50 High at ~02:10 High during evening twilight at ~19:20 1-
40o N Low in the northern sky in moonlight at ~21:00 High in moonlight at ~02:50 High at ~02:50 High at ~02:10 Fairly high during evening twilight at ~19:00 1-
Equator High in moonlight at ~04:50 Fairly high at ~03:10 Fairly high at ~02:50 Fairly high in the northern sky at ~02:10 Fairly high in the northern sky in moonlight at ~01:40 1-
30o S Low in the northern sky in moonlight at ~04:00 Not visible Not visible Not visible Not visible 1-7

C/2021 X1 (Maury-Attard): A morning comet visible in very large telescopes
This comet begins the month in Pisces at magnitude 14.7. Look for a 1.5' coma. It should remain constant.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible High in moonlight at ~02:00 High at ~01:20 High at ~00:30 Low in the eastern sky during evening twilight at ~19:30 3-27, 30-
40o N Not visible High at ~01:50 High at ~01:20 High at ~00:30 Low in the eastern sky during evening twilight at ~19:00 4-27, 30-
Equator Not visible High at ~02:00 High at ~01:20 High at ~01:00 Fairly high in the eastern sky at ~19:20 3-27, 30-
30o S Not visible High at ~02:00 High at ~01:20 High at ~02:00 Fairly high in the eastern sky at ~19:50 3-26, 30-

81P/Wild: An evening comet visible in very large telescopes
This comet begins the month in Ophiuchus at magnitude 15.1. Look for a 35" coma. It should fade by about 0.5 magnitudes by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Fairly high in the southern sky during evening twilight at ~20:00 Fairly high in the southern sky during evening twilight at ~19:50 Fairly high in the southern sky during evening twilight at ~19:40 Not visible Not visible 1-20
Equator High at ~19:20 High at ~19:20 High at ~19:10 Not visible High at ~19:10 1-21, 30-
30o S High at ~19:20 High at ~19:20 High at ~19:20 Not visible High at ~19:30 1-21, 30-

Summary Data for This Month's Telescopic Comets

Comets brighter than 16th magnitude.  This table is updated as necessary. The last column indicates the date of the last observation used to compute these values.  The constellation listed is where the comet was on the first of the month.
Comet Constellation

September 1st

September 15th

September 30th

 Observations as of (UT)
Mag Diam Mag Diam Mag Diam
C/2023 P1 (Nishimura) Cancer 6.6 5.0' 2.5 6.2' 6.3 3.9' 2023 August 28
C/2020 V2 (ZTF) Cetus 9.9 4.2' 9.9 4.4' 10.1 4.3' 2023 August 28
C/2023 E1 (ATLAS) Pegasus 10.9 4.8' 12.6 3.5' 14.5 2.5' 2023 August 28
C/2021 T4 (Lemmon) Libra 10.9 2.4' 11.6 2.0' 12.2 1.6' 2023 August 21
103P/Hartley Perseus 11.2 2.5' 10.4 2.9' 9.9 3.0' 2023 August 28
2P/Encke Auriga 11.4 2.5' 9.6 2.9' 7.3 3.0' 2023 August 27
12P/Pons-Brooks Draco 11.6 1.6' 11.4 1.7' 11.1 1.7' 2023 August 27
C/2021 S3 (PANSTARRS) Pyxis 12.6 46" 12.3 49" 12.0 52" 2023 August 25
C/2022 A2 (PANSTARRS) Pegasus 12.8 1.4' 13.1 1.3' 13.5 1.2' 2023 August 27
C/2017 K2 (PANSTARRS) Monoceros 13.0 1.4' 13.1 1.4' 13.3 1.4' 2023 August 25
237P/LINEAR Aquila 13.0 50" 13.3 45" 13.6 40" 2023 August 26
29P/Schwassmann-Wachmann Cancer 13.1 57" 13.0 59" 13.0 1.0' 2023 August 28
C/2020 K1 (PANSTARRS) Musca 13.5 1.2' 13.7 1.1' 13.9 1.0' 2023 August 25
C/2019 L3 (ATLAS) Antlia 13.7 51" 13.8 50" 13.9 49" 2023 July 14
185P/Petriew Cancer 13.8 2.1' 14.3 2.0' 14.8 1.9' 2023 August 19
C/2019 U5 (PANSTARRS) Hydra 14.3 53" 14.4 52" 14.5 52" 2023 July 14
C/2022 E3 (ZTF) Columba 14.3 2.3' 14.5 2.3' 14.6 2.3' 2023 August 19
C/2019 T4 (ATLAS) Serpens Caput 14.4 55" 14.5 53" 14.7 51" 2023 August 23
126P/IRAS Perseus 14.4 41" 14.6 42" 15.0 42" 2023 August 27
P/1906 UA (Scheila) Cetus 14.5 58" 14.5 59" 14.5 59" 2017 August 1
C/2021 X1 (Maury-Attard) Pisces 14.7 1.3' 14.6 1.4' 14.6 1.4' 2023 August 28
C/2021 Y1 (ATLAS) Vela 15.1? 2.1'? 15.4? 2.0'? 15.7? 1.9'? 2023 July 7
81P/Wild Ophiuchus 15.1 35" 15.4 31" 15.6 28" 2023 August 17
C/2022 JK5 (PANSTARRS) Sculptor 15.2 1.5' 15.3 1.4' 15.5 1.4' 2023 August 25
C/2021 G2 (Atlas) Hydra 15.3 51" 15.2 51" 15.2 51" 2023 July 15
C/2022 E2 (ATLAS) Hydra 15.4? 35"? 15.3? 36"? 15.1? 38"? 2023 July 8
C/2022 W3 (Leonard) Aquila 15.7 1.5' 16.8 1.1' 17.9 51" 2023 August 23
71P/Clark Cetus 15.8 1.3' 16.0 1.3' 16.3 1.3' 2023 August 17
C/2022 L2 (ATLAS) Virgo 15.9 38" 15.9 37" 16.0 36" 2023 August 19
C/2023 H2 (Lemmon) Ursa Major 15.9 41" 15.1 47" 14.0 59" 2023 August 22
C/2023 A3 (Tsuchinshan-ATLAS) Virgo 16.2 20" 16.1 20" 15.9 20" 2023 August 21
*In solar conjunction and generally not visible 

For information about specific comets see Gary W. Kronk's Cometography 

Further reading: see Comet Chasing, Sky & Telescope, April 2005, pg. 83.

Make your own visual observing custom charts for your location and telescope/binoculars: Software for visual comet observing 

Select comets that are appropriate for your imaging system, and plan when they are best imaged: Software for comet imaging 
 

Links

Skyhound's Guide to Comets
Skyhound's Guide to Finding Comets
BAA Comet Section
Weekly Information About Bright Comets
Cometography