Comet Chasing in January


Comet chasing is the visual observation of telescopic comets.

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January offers two comets visible in small telescopes.
  • C/2020 M3 (ATLAS) passed perihelion in late October. On October 25, this comet passed within 0.4 AU of the earth. It is currently predicted to attain maximum brightness of magnitude 7.5 in early November 9.

  • C/2020 S3 (Erasmus) passed perihelion on December 12 and is not observable. 

  • 11P/Tempel-Swift-LINEAR passed perihelion on November 25. 

  • 156P/Russell-LINEAR brightened rapidly and unexpected in October, and has since maintained at least magnitude 12.. This comet passed perihelion in mid November, when it will also be within 0.5 AU of the earth. 

  • C/2019 N1 (ATLAS) passed perihelion early December. It hasn't been observed since August. Based on the last observation, it is predicted to reach a maximum brightness of magnitude 9.7 in early January 2021.

  • C/2020 R4 (ATLAS) will reach perihelion in early March. It is currently predicted to reach maximum brightness of magnitude 6.8 in mid April.

  • 398P/Boattini passed perihelion in late December. On December 26 this comet will pass within 0.4 AU of the earth, when t is predicted to reach maximum brightness of magnitude 13.5.

  • 29P/Schwassmann-Wachmann had a very large outburst on November 19, becoming as bright as magnitude 12.8. This comet has frequent outbursts, 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/2019 L3 (ATLAS) will reach perihelion on 2022 January 9, when it may be magnitude 11.

  • C/2020 Q1 (Borisov) has apparently disintegrated.

  • C/2020 P1 (NEOWISE) passed perihelion on October 20 and has since disintegrated.

  • 88P/Howell passed perihelion in late September.

  • C/2020 F3 (NEOWISE) was a Great Comet that passed perihelion in early July. In late July this comet passed within 0.7 AU of the earth. 

  • 246P/NEAT will next reach perihelion in late February 2021. It is currently predicted to reach maximum brightness of magnitude 13.5 in late June of 2021..

  • C/2019 Y4 (ATLAS). This comet had the potential to become a bright naked-eye object near perihelion in late May, but on April 8 it was observed in images to have fragmented. It has not been observed since late May and is presumed lost. 

  • 2I/Borisov (formerly C/2019 Q4) is the first interstellar comet, discovered on August 30, 2019 by G. Borisov. It took until September 10/11 for the interstellar nature of this comet to become readily apparent. On September 24 the IAU officially recognized it as interstellar and assigned a new designation. It will reach perihelion in early December, when it will come within 1.9 AU of the sun and earth. At that time it will be in Hydra. It isn't yet clear how bright it will become, but with comets there is always the possibility that it will brighten enough to be observable visually in large instruments. More here...

C/2020 F3 (NEOWISE) on the evening of July 29, in moonlight, from Cloudcroft, New Mexcio.  

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!

Comet Synopses for January


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

11P/Tempel-Swift-LINEAR: An evening comet visible in small telescopes
This comet begins the month in Cetus at magnitude 9.9. Look for a 9.5' coma. It should fade by about 1.1 magnitudes, moving into Taurus by month's end.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 30 Nights Visible
55o N High at ~19:30 High at ~19:20 High at ~20:00 High in moonlight at ~19:00 High during evening twilight at ~18:40 1-
40o N High at ~19:30 High at ~19:20 High at ~20:30 High in moonlight at ~19:00 High at ~19:10 1-
Equator High at ~19:40 High at ~19:40 High in moonlight at ~19:40 High during evening twilight at ~19:30 High at ~19:40 1-
30o S High at ~20:50 High at ~20:40 High in moonlight at ~20:40 High during evening twilight at ~20:20 High at ~20:30 1-

156P/Russell-LINEAR: An evening comet visible in small telescopes
This comet begins the month in Pisces at magnitude 10.4. Look for a 4' coma. It should fade by about 1.1 magnitudes, moving into Triangulum by month's end.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 30 Nights Visible
55o N High at ~18:30 High at ~18:30 High at ~20:00 High during evening twilight at ~18:20 High during evening twilight at ~18:40 1-
40o N High at ~18:40 High at ~18:50 High in moonlight at ~18:50 High during evening twilight at ~18:40 High at ~19:00 1-
Equator High at ~19:30 High at ~19:30 High in moonlight at ~19:30 High during evening twilight at ~19:20 High at ~19:30 1-
30o S Fairly high in the northern sky during evening twilight at ~20:40 Fairly high in the northern sky during evening twilight at ~20:40 Low in the northern sky during evening twilight at ~20:30 Low in the northern sky during evening twilight at ~20:10 Low in the northern sky during evening twilight at ~20:20 1-

C/2019 N1 (ATLAS): A morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Centaurus at magnitude 10.8. Look for a 3.5' coma. It should fade slowly, moving into Triangulum Australe by month's end. The best visibility is mid-month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 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 1-4
Equator Fairly high during morning twilight at ~04:50 Fairly high in moonlight at ~04:50 Fairly high in the southern sky at ~04:50 Fairly high in the southern sky at ~04:50 Fairly high in the southern sky during morning twilight at ~05:10 1-
30o S High during morning twilight at ~03:40 High in moonlight at ~03:30 High at ~03:40 High at ~03:40 High during morning twilight at ~04:10 1-

398P/Boattini: An evening comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Eridanus at magnitude 11.0. Look for a 4' coma. It should fade by about 0.7 magnitudes, moving into Taurus by month's end.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 30 Nights Visible
55o N Fairly high in the southern sky at ~19:30 High at ~21:40 High at ~21:30 High in moonlight at ~21:00 High during evening twilight at ~18:40 1-
40o N High at ~20:20 High at ~21:40 High at ~21:30 High in moonlight at ~21:00 High at ~19:10 1-
Equator High at ~21:20 High at ~21:40 High at ~21:30 Low in the western sky at ~02:20 High at ~20:00 1-
30o S High at ~22:00 High at ~21:40 High at ~21:40 Low in the western sky at ~01:20 High at ~20:40 1-

C/2020 M3 (ATLAS): An evening comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Auriga at magnitude 10.6. Look for a 4.5' coma. It should fade rapidly.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 30 Nights Visible
55o N High at ~19:30 High at ~22:00 High at ~21:40 Fairly high in the western sky at ~04:30 High during evening twilight at ~18:40 1-
40o N High at ~20:20 High at ~22:00 High at ~21:40 Fairly high in the western sky at ~03:30 High at ~19:10 1-
Equator High at ~21:20 High at ~22:00 High at ~21:40 Very low in the northern sky at ~02:10 High at ~20:00 1-
30o S Low in the northern sky at ~22:00 Low in the northern sky at ~22:00 Low in the northern sky at ~21:40 Low in the northern sky in moonlight at ~21:10 Low in the northern sky at ~20:40 1-

88P/Howell: An evening comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Aquarius at magnitude 9.9. Look for a 5.5' coma. It should fade by about 1.3 magnitudes by month's end.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 30 Nights Visible
55o N Low in the southern sky during evening twilight at ~18:00 Low in the southern sky during evening twilight at ~18:00 Low in the western sky during evening twilight at ~18:10 Low in the western sky during evening twilight at ~18:10 Low in the western sky during evening twilight at ~18:30 1-
40o N Fairly high in the western sky at ~18:30 Fairly high in the western sky at ~18:30 Fairly high in the western sky during evening twilight at ~18:30 Fairly high in the western sky during evening twilight at ~18:30 Low in the western sky during evening twilight at ~18:50 1-
Equator Fairly high at ~19:20 Fairly high in the western sky at ~19:30 Fairly high in the western sky during evening twilight at ~19:20 Fairly high in the western sky during evening twilight at ~19:20 Fairly high in the western sky during evening twilight at ~19:30 1-
30o S Low in the western sky during evening twilight at ~20:40 Low in the western sky during evening twilight at ~20:30 Low in the western sky during evening twilight at ~20:20 Low in the western sky during evening twilight at ~20:10 Very low in the western sky during evening twilight at ~20:20 1-

141P/Machholz: An evening comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Aquarius at magnitude 11.0. Look for a 6' coma. It should fade rapidly, moving into Cetus by month's end.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 30 Nights Visible
55o N Fairly high in the southern sky at ~18:00 Fairly high in the southern sky at ~18:10 Fairly high in the southern sky in moonlight at ~18:20 Fairly high in the southern sky during evening twilight at ~18:20 Fairly high during evening twilight at ~18:40 1-
40o N Fairly high at ~18:30 Fairly high at ~18:30 Fairly high in moonlight at ~18:40 High during evening twilight at ~18:40 High at ~19:00 1-
Equator High at ~19:20 High at ~19:30 High in moonlight at ~19:30 High during evening twilight at ~19:20 High at ~19:30 1-
30o S 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 during evening twilight at ~20:40 High during evening twilight at ~20:20 High at ~20:30 1-

C/2020 R4 (ATLAS): An evening comet visible in a 14-inch (36 cm) telescope
This comet begins the month in Capricornus at magnitude 10.4. Look for a 3.5' coma. It should brighten by about 0.9 magnitudes by month's end.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 30 Nights Visible
55o N Very low in the southern sky during evening twilight at ~17:40 Very low in the western sky during evening twilight at ~17:30 Not visible Not visible Not visible 1-13
40o N Low in the western sky during evening twilight at ~18:20 Very low in the western sky during evening twilight at ~18:10 Very low in the western sky during evening twilight at ~18:00 Not visible Not visible 1-17
Equator Low in the western sky during evening twilight at ~19:20 Very low in the western sky during evening twilight at ~19:20 Very low in the western sky during evening twilight at ~19:00 Not visible Not visible 1-17
30o S Very low in the western sky during evening twilight at ~20:30 Very low in the western sky during evening twilight at ~20:10 Not visible Not visible Not visible 1-14

29P/Schwassmann-Wachmann: An evening comet visible in very large telescopes
This comet begins the month in Aries at magnitude 13.8. Look for a 55" coma. It should fade slowly.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 30 Nights Visible
55o N High at ~19:30 High at ~19:00 High at ~20:00 High during evening twilight at ~18:20 High during evening twilight at ~18:40 1-
40o N High at ~19:30 High at ~19:00 High in moonlight at ~18:50 High during evening twilight at ~18:40 High at ~19:00 1-
Equator High at ~19:40 High at ~19:40 High in moonlight at ~19:30 High during evening twilight at ~19:20 High at ~19:30 1-
30o S Fairly high at ~20:40 Fairly high at ~20:40 Fairly high in the northern sky during evening twilight at ~20:40 Fairly high in the northern sky during evening twilight at ~20:20 Fairly high in the northern sky during evening twilight at ~20:30 1-

C/2019 L3 (ATLAS): A northern hemisphere evening comet visible in very large telescopes
This comet begins the month in Cassiopeia at magnitude 13.9. Look for a 1.5' coma. It should remain constant.  FINDER CHART
Latitude Visibility January 2 Visibility January 9 Visibility January 16 Visibility January 23 Visibility January 30 Nights Visible
55o N High at ~18:20 High at ~18:20 High in moonlight at ~18:30 Fairly high in the northern sky at ~05:50 High during evening twilight at ~18:40 1-
40o N High at ~18:40 High at ~18:40 High in moonlight at ~18:40 High during evening twilight at ~18:40 High at ~19:00 1-
Equator Fairly high in the northern sky at ~19:20 Fairly high in the northern sky at ~19:30 Fairly high in the northern sky during evening twilight at ~19:30 Fairly high in the northern sky during evening twilight at ~19:20 Fairly high in the northern sky during evening twilight at ~19:30 1-
30o S Not visible Not visible Not visible Not visible Not visible  

Summary Data for This Month's Telescopic Comets


Comets brighter than 15th 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

January 1st

January 15th

January 31st

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
C/2020 S3 (Erasmus)* Scutum 8.1 3.5' 9.7 3.0' 11.0 2.6' 2020 November 29
88P/Howell Aquarius 9.9 5.5' 10.5 5.1' 11.2 4.7' 2020 December 17
C/2020 R4 (ATLAS) Capricornus 10.4 3.7' 10.0 3.6' 9.5 3.7' 2020 December 17
156P/Russell-LINEAR Pisces 10.4 4.3' 10.9 3.7' 11.6 3.1' 2020 December 17
C/2020 M3 (ATLAS) Auriga 10.6 4.6' 11.5 3.6' 12.4 2.8' 2020 December 17
141P/Machholz Aquarius 11.0 6.2' 12.0 7.0' 14.0 6.6' 2020 December 17
398P/Boattini Eridanus 11.0 4.0' 11.2 3.7' 11.7 3.1' 2020 December 17
11P/Tempel-Swift-LINEAR Cetus 11.3 5.1' 11.8 4.4' 12.4 3.7' 2020 December 17
29P/Schwassmann-Wachmann Aries 13.8 58" 13.9 55" 14.0 53" 2020 November 22
C/2019 L3 (ATLAS) Cassiopeia 13.9 33" 13.9 33" 13.8 32" 2020 December 15
C/2017 K2 (PANSTARRS) Hercules 14.8 1.3' 14.7 1.4' 14.5 1.4' 2020 November 24
C/2018 F4 (PANSTARRS) Cetus 14.9 45" 15.0 43" 15.2 40" 2020 December 17
C/2018 N2 (ASASSN) Draco 15.0 1.6' 15.1 1.6' 15.2 1.5' 2020 November 24
C/2020 F5 (MASTER) Indus 15.0 20" 15.0 20" 15.0 20" 2020 November 15
117P/Helin-Roman-Alu Virgo 15.1 43" 14.9 46" 14.6 50" 2015 November 12
*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 custom charts for your location and telescope/binoculars: software for visual comet observing

New: 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

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