Comet Chasing in October

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

News

There are three comets visible in small telescopes in October, but many more are visible in larger instruments.

  • 29P/Schwassmann-Wachmann had a very large outburst on September 25, brightening by over 3 magnitudes. As of October 1, it is visible in small telescopes, but it won't stay that way for long. This comet 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.

  • P/2021 Q5 (ATLAS) is a new discovery on August 29 by the ATLAS survey. This comet will passed perhileion on August 30.  

  • C/2021 O1 (Nishimura) is a new discovery on July 21 by H. Nishimura. It was found very low in morning twilight. It was low in the sky throughout August, reaching magnitude 9 on August 12 (at perihelion of 0.8 AU), but was difficult to observe. By the time it is observable again after the beginning of the year it will lilkely have faded. 

  • C/2014 UN271 (Bernardinelli-Bernstein) is an interesting Oort cloud comet that was recently 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 is unusually bright for its distance, so it is either intrinsically bright or unusually large for a comet. 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. 

  • C/2019 L3 (ATLAS) will reach perihelion on 2022 January 9, when it may be magnitude 11.

  • 4P/Faye passed perihelion in early September. It is currentlly predicted to reach maximum brightness in mid October.

  • 67P/Churyumov-Gerasimenko will next reach perihelion in early November. On November 2 this comet will pass within 0.4 AU of the earth when It is currently predicted to reach maximum brightness of magnitude 10.3. 

  • 15P/Finlay passed perihelion on July 13. 

  • 2020 T2 (Palomar) passed perihelion in mid July.  

  • 2020 J1 (SONEAR) passed perihelion in mid April.

  • C/2017 K2 (PANSTARRS) will reach perihelion in mid December 2022. It is predicted to reach maximum brightness of magnitude 6.5 in mid January 2023.

  • 6P/d'Arrest will next reach perihelion in mid September when it is predicted to reach maximum brightness of magnitude 10.8. 

  • 7P/Pons-Winnecke passed perihelion in late May. On May 27 this comet passed within 0.4 AU of the earth. It is currently predicted to reach maximum brightness of magnitude 11.2 in early June.

  • C/2020 R4 (Atlas) passed perihelion in early March. On March 1, this comet passed within 0.5 AU of the earth. This comet had an outburst in late April, brightening by as much as a magnitude. 

  • C/2021 A1 (Leonard) was discovered on January 3 by by G. J. Leonard at Mount Lemmon Observatory. It will reach perihelion on January 3, 2022. It may become visible to the naked eye in mid December 2021. It is currently very faint and not visualy observable. 

  • C/2021 A2 (NEOWISE) passed perihelion in late January. In early February this comet will pass within 0.5 AU of the earth. It is currently predicted to reach a maximum brightness of magnitude 11 in early February.

  • C/2021 A4 (NEOWISE) passed perihelion in mid-March.

  • 10P/Tempel passed perihelion in late March.

  • P/2016 J3 (STEREO) passed perihelion on January 25, when it passed within 0.5 AU of the earth. This comet unexpectedly returned early, based on the orbit that was calculated for it in 2016.

  • 246P/NEAT passed perihelion in late February 2021. It is currently predicted to reach maximum brightness of magnitude 14.7 in late June.

Comets that have apparently disentegrated: C/2020 Q1 (Borisov), C/2020 P1 (NEOWISE), and C/2019 Y4 (ATLAS). Beware that various other online 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 October

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

C/2019 L3 (ATLAS): A morning comet visible in small telescopes
This comet begins the month in Auriga at magnitude 10.5. Look for a 8.5' coma. It should brighten slowly, moving into Lynx by month's end.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N High in moonlight at ~04:00 High at ~04:20 High at ~04:30 High during morning twilight at ~05:00 High in moonlight at ~04:40 1-
40o N High in moonlight at ~04:30 High at ~04:30 High at ~04:40 High during morning twilight at ~05:00 High in moonlight at ~04:40 1-
Equator Fairly high during morning twilight at ~04:40 High during morning twilight at ~04:40 High during morning twilight at ~04:30 High during morning twilight at ~04:40 High in moonlight at ~04:30 1-
30o S Low in the northern sky during morning twilight at ~04:30 Low in the northern sky during morning twilight at ~04:20 Low in the northern sky during morning twilight at ~04:10 Low in the northern sky during morning twilight at ~04:00 Low in the northern sky during morning twilight at ~03:50 1-

67P/Churyumov-Gerasimenko: A morning comet visible in small telescopes
This comet begins the month in Taurus at magnitude 10.9. Look for a 3.5' coma. It should brighten by about 0.6 magnitudes, moving into Gemini by month's end.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N High in moonlight at ~03:50 High at ~04:00 High at ~04:10 High during morning twilight at ~05:00 High in moonlight at ~04:20 1-
40o N High in moonlight at ~04:10 High at ~04:20 High at ~04:20 High during morning twilight at ~05:00 High in moonlight at ~04:20 1-
Equator High in moonlight at ~04:10 High at ~04:20 High at ~04:20 High during morning twilight at ~04:40 High in moonlight at ~04:10 1-
30o S Fairly high at ~04:10 Fairly high at ~04:00 Fairly high at ~03:50 Fairly high during morning twilight at ~04:00 Fairly high in moonlight at ~03:40 1-

29P/Schwassmann-Wachmann: A morning comet visible in small telescopes
This comet begins the month in Auriga at magnitude 10.9. Look for a 1' coma. It should brighten slowly.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N High in moonlight at ~03:50 High at ~03:40 High at ~03:10 High in moonlight at ~03:30 High in moonlight at ~02:00 1-
40o N High in moonlight at ~04:10 High at ~03:40 High at ~03:10 High in moonlight at ~03:40 High at ~01:50 1-
Equator High in moonlight at ~04:10 High at ~03:40 High at ~03:20 High in moonlight at ~03:10 High at ~02:10 1-
30o S Fairly high in the northern sky at ~04:10 Fairly high in the northern sky at ~03:40 Fairly high in the northern sky at ~03:40 Fairly high in the northern sky in moonlight at ~02:50 Fairly high in the northern sky at ~02:20 1-

8P/Tuttle: A southern hemisphere morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Hydra at magnitude 9.6. Look for a 4' coma. It should fade rapidly, moving into Centaurus by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 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 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 ~04:40 Not visible Not visible 1-
30o S Low in the eastern sky during morning twilight at ~04:20 Low in the eastern sky during morning twilight at ~04:10 Low in the eastern sky during morning twilight at ~04:00 Low in the eastern sky during morning twilight at ~04:00 Low in the eastern sky during morning twilight at ~03:40 1-

C/2021 A1 (Leonard): A northern hemisphere morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Ursa Major at magnitude 12.9. Look for a 4' coma. It should brighten rapidly.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N Fairly high in the eastern sky in moonlight at ~04:00 Fairly high in the eastern sky at ~04:20 Fairly high at ~04:30 Fairly high during morning twilight at ~04:50 High in moonlight at ~05:00 1-
40o N Not visible Fairly high in the eastern sky during morning twilight at ~04:40 Fairly high at ~04:40 Fairly high during morning twilight at ~04:50 Fairly high in moonlight at ~04:50 1-
Equator Not visible Not visible Not visible Not visible Low in the eastern sky during morning twilight at ~04:40 13-
30o S Not visible Not visible Not visible Not visible Not visible  

4P/Faye: A morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Orion at magnitude 11.8. Look for a 2' coma. It should remain constant, moving into Monoceros by month's end.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N High in moonlight at ~04:00 High at ~04:10 High at ~04:20 High during morning twilight at ~04:50 High in moonlight at ~03:50 1-
40o N High in moonlight at ~04:20 High at ~04:20 High at ~04:30 Not visible High in moonlight at ~03:40 1-
Equator High in moonlight at ~04:30 High at ~04:30 High at ~04:20 Not visible High in moonlight at ~02:40 1-
30o S High at ~04:10 High at ~04:00 High at ~03:50 High during morning twilight at ~04:00 High at ~03:20 1-

C/2020 T2 (Palomar): An evening comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Scorpius at magnitude 11.3. Look for a 7' coma. It should fade by about 0.6 magnitudes, moving into Ophiuchus by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 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 ~19:00 Not visible Not visible Not visible Not visible 1-17, 20-22
Equator Fairly high at ~19:00 Fairly high in moonlight at ~19:00 Fairly high in the western sky during evening twilight at ~18:50 Fairly high in the western sky during evening twilight at ~19:00 Fairly high in the western sky during evening twilight at ~19:00 1-
30o S Fairly high at ~19:20 Fairly high in moonlight at ~19:30 Fairly high during evening twilight at ~19:30 Fairly high in the western sky during evening twilight at ~19:40 Fairly high in the western sky during evening twilight at ~19:50 1-

C/2017 K2 (PANSTARRS): An evening comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Hercules at magnitude 11.7. Look for a 2' coma. It should brighten slowly.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N High at ~19:40 High at ~19:20 High during evening twilight at ~18:50 Fairly high during evening twilight at ~18:30 Fairly high at ~18:30 1-
40o N High at ~19:10 High at ~19:00 High during evening twilight at ~18:50 High at ~18:40 Fairly high at ~18:30 1-
Equator High at ~19:00 Fairly high in moonlight at ~19:00 Fairly high during evening twilight at ~19:00 Fairly high in the western sky during evening twilight at ~19:00 Fairly high in the western sky during evening twilight at ~19:00 1-
30o S Low in the northern sky during evening twilight at ~19:20 Low in the western sky during evening twilight at ~19:20 Low in the western sky during evening twilight at ~19:20 Not visible Not visible 1-26

19P/Borrelly: A southern hemisphere evening comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Tucana at magnitude 13.9. Look for a 1.5' coma. It should brighten by about 1.4 magnitudes, moving into Grus by month's end. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 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 Fairly high at ~22:40 Fairly high at ~22:00 Fairly high in moonlight at ~21:30 Fairly high at ~20:30 Fairly high at ~20:30 1-
30o S High at ~22:40 High at ~22:00 Fairly high in the southern sky at ~03:30 High at ~21:00 High at ~20:30 1-

P/2021 Q5 (ATLAS): A morning comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Cancer at magnitude 14.1. Look for a 5" coma. It should fade slowly, moving into Sextans by month's end.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N Fairly high in the eastern sky during morning twilight at ~04:20 Fairly high in the eastern sky during morning twilight at ~04:30 Fairly high during morning twilight at ~04:40 Fairly high during morning twilight at ~05:00 Fairly high during morning twilight at ~05:10 1-
40o N Fairly high during morning twilight at ~04:30 Fairly high during morning twilight at ~04:40 Fairly high during morning twilight at ~04:50 High during morning twilight at ~05:00 High during morning twilight at ~05:00 1-
Equator Fairly high during morning twilight at ~04:40 Fairly high during morning twilight at ~04:40 High during morning twilight at ~04:30 High during morning twilight at ~04:40 High during morning twilight at ~04:30 1-
30o S Fairly high in the eastern sky during morning twilight at ~04:20 Fairly high in the eastern sky during morning twilight at ~04:20 Fairly high in the eastern sky during morning twilight at ~04:10 Fairly high in the eastern sky during morning twilight at ~04:00 Fairly high in the eastern sky during morning twilight at ~03:50 1-

C/2018 U1 (Lemmon): An evening comet visible in an 18-inch (46 cm) telescope
This comet begins the month in Scorpius at magnitude 14.3. Look for a 20" coma. It should fade slowly, moving into Ophiuchus by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 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 ~19:00 Low in the western sky during evening twilight at ~18:50 Not visible Not visible Not visible 1-14, 16-16
Equator Fairly high at ~19:00 Fairly high during evening twilight at ~19:00 Fairly high in the western sky during evening twilight at ~18:50 Low in the western sky during evening twilight at ~18:50 Low in the western sky during evening twilight at ~18:50 1-
30o S Fairly high at ~19:20 Fairly high during evening twilight at ~19:30 Fairly high in the western sky during evening twilight at ~19:30 Low in the western sky during evening twilight at ~19:30 Low in the western sky during evening twilight at ~19:40 1-

6P/d'Arrest: An evening comet visible in very large telescopes
This comet begins the month in Sagittarius at magnitude 11.9. Look for a 4' coma. It should fade by about 1.4 magnitudes, moving into Microscopium by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 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 ~19:00 Low in the southern sky during evening twilight at ~18:50 Not visible Low in the southern sky during evening twilight at ~18:30 Not visible 1-12, 22-28
Equator High at ~19:10 High in moonlight at ~19:10 Not visible High at ~19:10 High at ~19:10 1-13, 20-
30o S High at ~19:30 High in moonlight at ~19:40 Not visible High at ~19:50 High at ~20:00 1-13, 20-

15P/Finlay: A northern hemisphere morning comet visible in very large telescopes
This comet begins the month in Cancer at magnitude 13.4. Look for a 5.5' coma. It should fade by about 0.7 magnitudes by month's end.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N High in moonlight at ~04:00 Not visible Not visible Not visible Not visible 2-7
40o N High in moonlight at ~04:20 High at ~04:30 Not visible Not visible Not visible 1-11
Equator High in moonlight at ~04:30 Not visible Not visible Not visible Not visible 2-3
30o S Not visible Not visible Not visible Not visible Not visible  

7P/Pons-Winnecke: A southern hemisphere evening comet visible in very large telescopes
This comet begins the month in Grus at magnitude 13.6. Look for a 5.5' coma. It should fade by about 1.4 magnitudes by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 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 High at ~22:30 High at ~22:00 Not visible High at ~20:10 Not visible 1-13, 22-29
30o S High at ~22:30 High at ~22:00 Not visible High at ~21:00 High at ~20:40 1-14, 21-

108P/Ciffreo: A morning comet visible in very large telescopes
This comet begins the month in Gemini at magnitude 13.9. Look for a 1' coma. It should fade slowly.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N High in moonlight at ~04:00 High at ~04:10 High at ~04:20 High during morning twilight at ~05:00 High in moonlight at ~04:00 1-
40o N High in moonlight at ~04:20 High at ~04:30 High at ~04:30 High during morning twilight at ~05:00 High in moonlight at ~03:50 1-
Equator High in moonlight at ~04:30 High at ~04:30 High at ~04:20 High during morning twilight at ~04:40 High in moonlight at ~03:50 1-
30o S Fairly high at ~04:10 Fairly high at ~04:00 Fairly high at ~03:50 Fairly high during morning twilight at ~03:50 Fairly high in the northern sky in moonlight at ~03:40 1-

C/2019 T4 (ATLAS): A morning comet visible in very large telescopes
This comet begins the month in Hydra at magnitude 14.3. Look for a 30" coma. It should brighten slowly. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 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 31-
Equator Not visible Low in the eastern sky during morning twilight at ~04:40 Low in the eastern sky during morning twilight at ~04:40 Fairly high in the eastern sky during morning twilight at ~04:40 Fairly high in the eastern sky during morning twilight at ~04:30 3-
30o S Low in the eastern sky during morning twilight at ~04:20 Low in the eastern sky during morning twilight at ~04:10 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 in the eastern sky during morning twilight at ~03:40 1-

C/2020 PV6 (PANSTARRS): A northern hemisphere evening comet visible in very large telescopes
This comet begins the month in Hercules at magnitude 14.2. Look for a 2.5' coma. It should fade slowly.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N Fairly high at ~19:40 Fairly high in the western sky at ~19:20 Fairly high in the western sky during evening twilight at ~18:50 Fairly high in the western sky during evening twilight at ~18:40 Fairly high in the western sky during evening twilight at ~18:30 1-16, 22-
40o N Fairly high at ~19:10 Fairly high at ~19:00 Not visible Fairly high in the western sky during evening twilight at ~18:40 Fairly high in the western sky during evening twilight at ~18:30 1-15, 21-
Equator Fairly high at ~19:00 Fairly high in the western sky during evening twilight at ~19:00 Not visible Not visible Not visible 1-13
30o S Not visible Not visible Not visible Not visible Not visible  

C/2020 F5 (MASTER): An evening comet visible in very large telescopes
This comet begins the month in Pisces Austrinus at magnitude 14.4. Look for a 2' coma. It should fade slowly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Fairly high in the southern sky at ~21:50 Fairly high in the southern sky at ~21:20 Not visible Fairly high in the southern sky at ~19:20 Fairly high in the southern sky at ~19:50 1-14, 20-
Equator High at ~21:50 High at ~21:20 Not visible High at ~20:20 High at ~19:50 1-14, 20-
30o S High at ~21:50 High at ~21:20 Not visible High at ~20:20 High at ~19:50 1-15, 20-

284P/McNaught: An evening comet visible in very large telescopes
This comet begins the month in Aquarius at magnitude 14.8. Look for a 35" coma. It should fade slowly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 30 Nights Visible
55o N Low in the southern sky at ~22:20 Low in the southern sky at ~21:50 Low in the southern sky in moonlight at ~21:20 Low in the southern sky in moonlight at ~20:10 Low in the southern sky at ~20:30 1-16, 18-
40o N Fairly high at ~22:20 Fairly high at ~21:50 Not visible Fairly high in the southern sky at ~19:10 Fairly high at ~20:30 1-15, 19-
Equator High at ~22:20 High at ~21:50 Not visible High at ~20:10 High at ~20:30 1-15, 19-
30o S High at ~22:20 High at ~21:50 Not visible High at ~21:00 High at ~20:30 1-15, 19-

C/2019 F1 (ATLAS-Africano): A southern hemisphere evening comet visible in very large telescopes
This comet begins the month in Octans at magnitude 14.9. Look for a 45" coma. It should fade slowly, moving into Indus by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART

Latitude Visibility October 2 Visibility October 9 Visibility October 16 Visibility October 23 Visibility October 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 Low in the southern sky at ~20:20 Low in the southern sky in moonlight at ~20:00 Low in the southern sky in moonlight at ~19:30 Low in the southern sky at ~19:20 Low in the southern sky at ~19:10 1-
30o S High at ~20:20 High in moonlight at ~20:00 Fairly high in the southern sky at ~03:30 High during evening twilight at ~19:40 High during evening twilight at ~19:40 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

October 1st

October 15th

October 31st

 Observations as of (UT)
Mag Diam Mag Diam Mag Diam
8P/Tuttle Hydra 9.6 4.0' 10.5 3.8' 11.6 3.5' 2021 September 18
C/2019 L3 (ATLAS) Auriga 10.5 7.3' 10.3 7.8' 10.1 8.4' 2021 September 23
67P/Churyumov-Gerasimenko Taurus 10.9 2.9' 10.5 3.2' 10.3 3.4' 2021 September 30
29P/Schwassmann-Wachmann Auriga 10.9 1.1' 10.8 1.1' 10.8 1.2' 2021 September 30
C/2021 O1 (Nishimura)* Virgo 11.3? 1.0'? 12.1? 57"? 12.9? 52"? 2021 July 26
C/2020 T2 (Palomar) Scorpius 11.3 7.0' 11.6 6.5' 11.9 6.0' 2021 September 16
C/2017 K2 (PANSTARRS) Hercules 11.7 2.2' 11.6 2.2' 11.5 2.2' 2021 September 29
4P/Faye Orion 11.8 2.0' 11.8 2.2' 11.8 2.3' 2021 September 30
6P/d'Arrest Sagittarius 11.9 4.0' 12.5 3.7' 13.4 3.2' 2021 September 22
C/2021 A1 (Leonard) Ursa Major 12.9 2.6' 12.0 3.0' 10.7 4.0' 2021 September 23
15P/Finlay Cancer 13.4 5.4' 13.8 5.4' 14.2 5.5' 2021 September 23
7P/Pons-Winnecke Grus 13.6 5.8' 14.3 5.0' 15.1 4.2' 2021 September 15
19P/Borrelly Tucana 13.9 1.6' 13.3 1.6' 12.5 1.7' 2021 September 18
C/2020 J1 (SONEAR) Virgo 13.9 2.3' 14.1 2.2' 14.2 2.2' 2021 September 17
108P/Ciffreo Gemini 13.9 1.1' 14.0 1.2' 14.1 1.3' 2021 September 18
P/2021 Q5 (ATLAS) Cancer 14.1 6" 14.2 6" 14.5 6" 2021 September 15
C/2020 PV6 (PANSTARRS) Hercules 14.2 2.5' 14.4 2.3' 14.6 2.2' 2021 September 28
C/2019 T4 (ATLAS) Hydra 14.3? 27"? 14.2? 27"? 14.1? 28"? 2021 July 12
C/2018 U1 (Lemmon) Scorpius 14.3 19" 14.4 18" 14.5 18" 2021 September 8
C/2020 F5 (MASTER) Pisces Austrinus 14.4 2.0' 14.6 1.9' 14.7 1.8' 2021 September 15
132P/Helin-Roman-Alu Pisces 14.8 1.1' 14.7 1.1' 14.7 1.0' 2021 September 26
284P/McNaught Aquarius 14.8 37" 15.0 34" 15.2 31" 2021 September 12
C/2019 F1 (ATLAS-Africano) Octans 14.9 43" 15.0 42" 15.2 40" 2021 September 12
252P/LINEAR Libra 15.0 3.7' 15.5 3.4' 16.1 3.2' 2021 September 18
C/2020 M5 (ATLAS) Coma Berenices 15.2 2.0' 15.2 2.0' 15.2 2.0' 2021 September 10
246P/NEAT Sagittarius 15.2 25" 15.4 23" 15.6 22" 2021 August 10
17P/Holmes Auriga 15.5 2.0' 15.6 2.1' 15.6 2.2' 2021 September 23
70P/Kojima Cancer 15.5 11" 15.4 12" 15.2 13" 2015 March 19
22P/Kopff* Virgo 15.6 41" 15.1 42" 14.6 43" 2021 June 30
C/2021 K1 (ATLAS) Cetus 15.6 32" 15.8 30" 16.1 28" 2021 September 16
117P/Helin-Roman-Alu Libra 15.7 1.2' 15.6 1.2' 15.6 1.2' 2021 September 1
C/2021 A7 (NEOWISE) Coma Berenices 15.7? 1.8'? 15.9? 1.9'? 16.0? 1.9'? 2021 July 9
C/2020 Y2 (ATLAS) Hydra 15.9? 21"? 15.8? 21"? 15.6? 22"? 2021 June 13
193P/LINEAR-NEAT Pisces 15.9 1.1' 16.1 59" 16.4 53" 2021 September 13
C/2021 E3 (ZTF) Hercules 16.1 32" 16.0 31" 15.8 30" 2021 September 26
C/2020 R7 (ATLAS) Hydrus 16.1 1.0' 16.0 1.0' 15.9 1.0' 2021 September 18
C/2020 U5 (PANSTARRS) Ursa Major 16.2 26" 16.0 27" 15.8 29" 2021 September 11
C/2020 V2 (ZTF) Canes Venatici 16.3 43" 16.2 45" 16.0 46" 2021 September 9
*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