Comet Chasing in July


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

This month there are three comets visible in binoculars and small telescopes. Many more are visible in larger instruments. See the Observing Synopses for which comets are visible from your latitude, the best dates and the time of night.
  • Comet 12P/Pons-Brooks passed perihelion on April 21 and has become a southern-hemisphere object. It continues to impress in images, now showing a small dust tail. This well-documented comet, perhaps observed as early as the year 245, experienced a large unexpected outburst in late July 2023, catapulting from a magnitude of 16.6 to 11.6 in a single day. Afterward it displayed an unusual coma shape, characterized by a distinctive 'notch' and a pair of 'horns' that persisted for weeks. The same pattern repeated in the following months, except in recent outbursts the 'horns' have become longer and crived.  Here is a link to a video with an animation of the July outburst aftermath 

  • 13P/Olbers will passed perihelion in late June. It is predicted to obtain maximum brightness of magnitude ~5 in early July.

  • C/2023 A3 (Tsuchinshan-ATLAS) has the potential to be a bright, possibly naked eye, comet in the fall. It will reach perihelion on September 28, 2024.

  • C/2021 S3 (PANSTARRS) passed perihelion in mid February 2024. It is now fading slowly, but continues to display a nce tail in images.  

  • C/2023 V4 (Camarasa-Duszanowicz) is past perihelion, which occurred in late May 2024. It is predicted to reach maximum brightness of magnitude 11.2 in early June.

  • C/2021 G2 (Atlas) will reach perihelion in early September. It is currently predicted to reach maximum brightness of magnitude 14.3 in late August. 

  • 479P/Elenin passed perihelion in early May. Also in early May this comet passed within 0.6 AU of the earth.

  • C/2023 C2 (ATLAS) will reach perihelion in mid November. It is predicted to reach maximum brightness of magnitude 13.5 in late October.

  • C/2023 R2 (PANSTARRS) will reach perihelion on August 12. It is predicted to reach maximum brightness of magnitude 11.5 in mid August.

  • 62P/Tsuchinshan passed perihelion in late December. In late January 2024, this comet passed within 0.5 AU of the earth. 

  • 144P/Kushida passed perihelion in late January 2024. In January magnitude estimates were about 1.5 magnitude brighter than previous. This comet has an orbital period of 7.5 years and is now on its way out of the inner solar system.  It will next reach perihelion in late July 2031.

  • 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. 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! The predictions are makde for a Country/Suburban site, which is Bortle 5, unless indicated otherwse.

Observing Synopses for July


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

13P/Olbers: An evening comet visible in binoculars
This comet begins the month in Lynx at magnitude 6.8. Look for a 3.5' coma, condensation is a diffuse spot in coma center; moderately condensed. It should fade by about 0.7 magnitudes, moving into Ursa Major by month's end.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 Nights Visible
55o N Low in the northern sky during evening twilight at ~22:50 Low in the northern sky during evening twilight at ~22:40 Low in the northern sky during evening twilight at ~22:30 Low in the western sky during evening twilight at ~22:20 Low in the western sky during evening twilight at ~22:00 1-
40o N Low in the western sky during evening twilight at ~20:50 Low in the western sky 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 ~20:40 Fairly high in the western sky during evening twilight at ~20:30 1-
Equator Low in the western sky during evening twilight at ~18:50 Low in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~19:00 1-
30o S Not visible Not visible Not visible Not visible Not visible 26-27, 29-

12P/Pons-Brooks: A southern hemisphere evening comet visible in binoculars at a dark site, or a small telescope under a country sky
This comet begins the month in Puppis at magnitude 8.0. Look for a 6' coma, condensation is a diffuse spot in coma center; moderately condensed. It should fade rapidly, moving into Vela by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 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 western sky during evening twilight at ~18:20 Fairly high in the western sky during evening twilight at ~18:30 Fairly high in the western sky during evening twilight at ~18:30 Fairly high during evening twilight at ~18:30 Fairly high during evening twilight at ~18:40 1-

C/2023 A3 (Tsuchinshan-ATLAS): An evening comet visible in small telescopes
This comet begins the month in Leo at magnitude 9.9. Look for a 2' coma, condensation is a diffuse spot in coma center; moderately condensed. It should brighten by about 1.3 magnitudes by month's end. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Fairly high in the western sky during evening twilight at ~21:00 Low in the western sky during evening twilight at ~21:00 Low in the western sky during evening twilight at ~20:40 Not visible Not visible 1-21
Equator High during evening twilight at ~19:20 High during evening twilight at ~19:20 Fairly high during evening twilight 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 1-
30o S High during evening twilight at ~18:30 High during evening twilight at ~18:30 Fairly high during evening twilight at ~18:30 Fairly high during evening twilight at ~18:30 Fairly high in the western sky during evening twilight at ~18:40 1-

C/2021 S3 (PANSTARRS): A northern hemisphere morning comet visible in a 10-inch (25 cm) telescope at a dark site
This comet begins the month in Draco at magnitude 12.7. Look for a 1' coma, center much brighter than edges, though still diffuse. It should fade by about 0.6 magnitudes by month's end.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 Nights Visible
55o N High during morning twilight at ~00:10 High during morning twilight at ~00:10 High during morning twilight at ~00:10 High during morning twilight at ~00:20 High during evening twilight at ~23:30 1-
40o N High at ~00:50 High at ~01:00 High at ~00:20 High during morning twilight at ~03:10 High at ~23:00 1-
Equator Fairly high in the northern sky at ~01:30 Fairly high in the northern sky at ~01:00 Fairly high in the northern sky at ~00:30 Not visible Not visible 1-
30o S Not visible Not visible Not visible Not visible Not visible  

C/2023 C2 (ATLAS): A southern hemisphere evening comet visible in a 10-inch (25 cm) telescope at a dark site, or a 24-inch telescope under a country sky
This comet begins the month in Triangulum Australe at magnitude 13.7. Look for a 45" coma, condensation is a diffuse spot in coma center; moderately condensed. It should brighten slowly, moving into Norma by month's end. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 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 Fairly high in the southern sky in moonlight at ~20:00 Not visible Fairly high in the southern sky at ~19:30 1-
30o S High at ~20:50 High at ~20:30 High in moonlight at ~20:30 High during evening twilight at ~18:30 High at ~19:20 1-

C/2023 V4 (Camarasa-Duszanowicz): A far-northern evening comet visible in a 14-inch (36 cm) telescope at a dark site
This comet begins the month in Lynx at magnitude 11.3. Look for a 3' coma, diffuse condensation at center. It should fade by about 1.2 magnitudes, moving into Ursa Major by month's end.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible 1-
40o N Fairly high in the northern sky during evening twilight at ~21:20 Fairly high in the northern sky during evening twilight at ~21:20 Fairly high in the northern sky during evening twilight at ~21:10 Fairly high during evening twilight at ~21:00 Fairly high during evening twilight at ~21:00 1-
Equator Not visible Not visible Not visible Not visible Not visible  
30o S Not visible Not visible Not visible Not visible Not visible  

C/2021 G2 (Atlas): A southern hemisphere evening comet visible in a 16-inch (41 cm) telescope at a dark site
This comet begins the month in Corvus at magnitude 14.0. Look for a 55" coma, condensation is a diffuse spot in coma center; moderately condensed. It should fade slowly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 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 High during evening twilight at ~19:20 High during evening twilight at ~19:20 High during evening twilight at ~19:20 High during evening twilight at ~19:10 Fairly high during evening twilight at ~19:20 1-
30o S High at ~18:40 High during evening twilight at ~18:40 High during evening twilight at ~18:40 High during evening twilight at ~18:30 High during evening twilight at ~18:40 1-

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

July 1st

July 15th

July 31st

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
13P/Olbers Lynx 6.8 3.4' 7.0 3.5' 7.6 3.5' 2024 July 1
12P/Pons-Brooks Puppis 8.0 6.1' 8.8 5.7' 9.7 5.0' 2024 June 30
C/2023 A3 (Tsuchinshan-ATLAS) Leo 9.9 2.1' 9.4 2.0' 8.6 2.0' 2024 July 1
C/2023 V4 (Camarasa-Duszanowicz) Lynx 11.3 2.9' 11.7 2.9' 12.5 2.7' 2024 June 29
C/2021 S3 (PANSTARRS) Draco 12.7 1.1' 13.0 1.1' 13.4 1.0' 2024 June 29
C/2023 R2 (PANSTARRS) Monoceros 13.4 33" 12.7 35" 12.2 37" 2024 May 1
154P/Brewington Perseus 13.7 54" 13.9 55" 14.3 55" 2024 June 18
C/2023 C2 (ATLAS) Triangulum Australe 13.7 46" 13.6 47" 13.4 46" 2024 June 24
C/2020 V2 (ZTF) Phoenix 13.8 1.5' 13.9 1.5' 14.0 1.5' 2024 June 18
C/2021 G2 (Atlas) Corvus 14.0 57" 14.1 54" 14.2 52" 2024 June 30
C/2022 E2 (ATLAS) Auriga 14.1 41" 14.1 41" 14.0 42" 2024 May 29
29P/Schwassmann-Wachmann Cancer 14.5 1.3' 14.5 1.3' 14.5 1.3' 2024 June 12
479P/Elenin Hydra 14.5 51" 15.1 44" 15.9 36" 2024 June 19
130P/McNaught-Hughes Pisces 15.1 51" 15.1 53" 15.2 57" 2024 June 20
32P/Comas Sola Cancer 15.3 46" 15.5 45" 15.8 43" 2024 May 13
C/2017 K2 (PANSTARRS) Orion 15.5 45" 15.6 45" 15.6 45" 2024 April 12
C/2019 U5 (PANSTARRS) Puppis 15.5 22" 15.6 21" 15.7 21" 2024 June 7
473P/NEAT Ursa Major 15.7 1.6' 16.1 1.5' 16.5 1.4' 2024 June 25
C/2022 L2 (ATLAS) Hydra 15.9 26" 16.1 24" 16.3 22" 2024 June 13
C/2019 T4 (ATLAS) Hercules 15.9 46" 16.0 45" 16.1 44" 2024 June 27
299P/Catalina-PANSTARRS Libra 16.0 29" 16.1 27" 16.3 25" 2024 June 28
C/2022 N2 (PANSTARRS) Aquarius 16.1 33" 15.9 35" 15.7 37" 2024 June 24
*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