Comet Chasing in January Comet chasing is the visual
observation of telescopic comets.
January offers two comets visible in small
telescopes.
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 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 156P/Russell-LINEAR: An
evening comet visible in small telescopes C/2019 N1 (ATLAS): A
morning comet visible in a 6-inch (15 cm) telescope 398P/Boattini: An evening
comet visible in a 6-inch (15 cm) telescope C/2020 M3 (ATLAS): An
evening comet visible in an 8-inch (20 cm) telescope 88P/Howell: An evening
comet visible in a 10-inch (25 cm) telescope 141P/Machholz: An evening
comet visible in a 10-inch (25 cm) telescope C/2020 R4 (ATLAS): An
evening comet visible in a 14-inch (36 cm) telescope 29P/Schwassmann-Wachmann:
An evening comet visible in very large telescopes C/2019 L3 (ATLAS): A
northern hemisphere evening comet visible in very large 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-
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-
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-
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-
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-
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-
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-
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
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-
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
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 |
For information about specific comets see Gary W. Kronk's Cometography
Further reading: see Comet Chasing, Sky & Telescope, April 2005, pg. 83.
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