Comet Chasing in April Comet chasing is the visual
observation of telescopic comets. Jump to: Observing
synopses Summary data
February offers an excitring new discovery and three comets visible in
a six-inch telescope.
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 an outburst on January 15. 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. 88P/Howell passed perihelion in late September 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... Comets that have apparently disentegrated: C/2020 Q1 (Borisov), C/2020 P1 (NEOWISE). Beware that various 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 April
Explanation
of Comet Synopses and charts (read this if you have questions) C/2020 R4 (ATLAS): A
morning comet visible in binoculars C/2019 L3 (ATLAS): A
northern hemisphere evening comet visible in an 8-inch (20 cm) telescope C/2020 T2 (Palomar): An
evening comet visible in an 8-inch (20 cm) telescope C/2020 J1 (SONEAR): A
morning comet visible in an 8-inch (20 cm) telescope 10P/Tempel: A southern
hemisphere morning comet visible in a 10-inch (25 cm) telescope 246P/NEAT: A morning comet
visible in a 12.5-inch (32 cm) telescope C/2017 K2 (PANSTARRS): A
morning comet visible in a 12.5-inch (32 cm) telescope 7P/Pons-Winnecke: A
morning comet visible in an 18-inch (46 cm) telescope C/2021 D1 (SWAN): A
northern hemisphere evening comet visible in very large telescopes C/2020 S3 (Erasmus): A
southern hemisphere morning comet visible in very large telescopes C/2021 A4 (NEOWISE): A
southern hemisphere evening comet visible in very large telescopes C/2019 N1 (ATLAS): A
southern hemisphere evening comet visible in very large telescopes C/2019 T4 (ATLAS): An
evening comet visible in very large telescopes C/2019 F1
(ATLAS-Africano): A southern hemisphere morning comet visible in very large
telescopes
This comet begins the month in Aquila at magnitude 9.1. Look for
a 8' coma. It should brighten slowly, moving into Bootes by month's end. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
Nights Visible
55o
N
Fairly high in the eastern sky
during morning twilight at ~03:20
Fairly high during morning
twilight at ~02:50
High at ~02:10
High during morning twilight at
~02:30
High at ~23:20
1-
40o
N
Fairly high in moonlight at
~03:40
High at ~03:50
High at ~03:20
High during morning twilight at
~03:50
High at ~22:50
1-
Equator
High in moonlight at ~04:10
High at ~04:40
High at ~04:00
High at ~04:10
High at ~22:50
1-
30o S
High in moonlight at ~04:40
High at ~04:50
High at ~04:00
Fairly high in the northern sky
at ~03:50
Fairly high in the northern sky
at ~22:00
1-
This comet begins the month in Perseus at magnitude 11.6. Look
for a 1.5' coma. It should brighten slowly. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
Nights Visible
55o
N
Fairly high during evening
twilight at ~20:50
Fairly high in the northern sky
during evening twilight at ~21:10
Fairly high in the northern sky
during evening twilight at ~21:30
Fairly high in the northern sky
during evening twilight at ~21:50
Low in the northern sky during
evening twilight at ~22:20
1-
40o
N
Fairly high in the northern sky
during evening twilight at ~20:00
Fairly high in the northern sky
during evening twilight at ~20:10
Fairly high in the northern sky
during evening twilight at ~20:10
Low in the northern sky during
evening twilight at ~20:20
Low in the northern sky during
evening twilight at ~20:30
1-
Equator
Not visible
Not visible
Not visible
Not visible
Not visible
1-1
30o S
Not visible
Not visible
Not visible
Not visible
Not visible
This comet begins the month in Canes Venatici at magnitude 12.7.
Look for a 1.5' coma. It should brighten slowly. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
Nights Visible
55o
N
High at ~01:10
High at ~00:40
High at ~00:20
High during morning twilight at
~02:30
High at ~23:20
1-
40o
N
High at ~01:10
High at ~00:40
High at ~00:10
High during morning twilight at
~03:40
High at ~23:10
1-
Equator
High at ~00:10
High at ~00:40
High at ~00:10
Fairly high in the western sky
at ~03:50
High at ~22:50
1-
30o S
Fairly high in the northern sky
in moonlight at ~01:00
Fairly high in the northern sky
at ~00:40
Fairly high in the northern sky
at ~00:10
Fairly high in the northern sky
in moonlight at ~00:00
Fairly high in the northern sky
at ~22:10
1-
This comet begins the month in Scorpius at magnitude 13.3. Look
for a 35" coma. It should brighten slowly. The best visibility is late in
the month as seen from the southern hemisphere. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
Nights Visible
55o
N
Not visible
Not visible
Not visible
Not visible
Not visible
40o
N
Not visible
Low in the southern sky at
~03:40
Low in the southern sky at
~03:00
Low in the southern sky in
moonlight at ~02:30
Low in the southern sky at
~01:10
1-
Equator
High in moonlight at ~04:00
High at ~03:40
High at ~03:00
High at ~04:10
High at ~23:00
1-
30o S
High in moonlight at ~04:20
High at ~03:40
High at ~03:00
High at ~04:10
High at ~22:00
1-
This comet begins the month in Aquarius at magnitude 10.6. Look
for a 2' coma. It should fade slowly, moving into Pisces by month's end. The
best visibility is late in the month as seen from the southern hemisphere.
FINDER CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
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 ~05:00
Low in the eastern sky during
morning twilight at ~05:00
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
Low in the eastern sky during
morning twilight at ~05:00
Low in the eastern sky during
morning twilight at ~05:00
Low in the eastern sky during
morning twilight at ~05:10
Low in the eastern sky during
morning twilight at ~05:10
Fairly high in the eastern sky
during morning twilight at ~05:10
1-
This comet begins the month in Sagittarius at magnitude 13.6.
Look for a 45" coma. It should brighten slowly. The best visibility is late
in the month as seen from the southern hemisphere. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
Nights Visible
55o
N
Not visible
Not visible
Not visible
Not visible
Not visible
40o
N
Low in the southern sky during
morning twilight at ~04:10
Fairly high in the southern sky
during morning twilight at ~04:00
Fairly high in the southern sky
during morning twilight at ~03:50
Fairly high in the southern sky
during morning twilight at ~03:40
Fairly high in the southern sky
during morning twilight at ~03:20
1-
Equator
High in moonlight at ~04:50
High at ~04:40
High at ~04:40
High at ~04:30
High during morning twilight at
~04:40
1-
30o S
High in moonlight at ~04:40
High at ~04:50
High at ~04:50
High at ~05:00
High during morning twilight at
~05:10
1-
This comet begins the month in Lyra at magnitude 14.1. Look for
a 25" coma. It should brighten slowly. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
Nights Visible
55o
N
High at ~03:00
High at ~02:40
High at ~02:10
High during morning twilight at
~02:30
High during morning twilight at
~01:10
1-
40o
N
High at ~02:10
High at ~03:40
High at ~03:30
High during morning twilight at
~03:40
High at ~00:40
1-
Equator
High in moonlight at ~04:40
High at ~04:40
High at ~04:40
High at ~04:10
High in moonlight at ~03:00
1-
30o S
Low in the northern sky in
moonlight at ~04:50
Low in the northern sky during
morning twilight at ~05:00
Low in the northern sky at
~04:40
Low in the northern sky at
~04:10
Low in the northern sky in
moonlight at ~03:40
1-
This comet begins the month in Ophiuchus at magnitude 13.3. Look
for a 6.5' coma. It should brighten by about 1.3 magnitudes, moving into Aquila
by month's end. FINDER CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
Nights Visible
55o
N
Fairly high at ~03:10
Fairly high during morning
twilight at ~02:50
Fairly high during morning
twilight at ~02:30
Fairly high during morning
twilight at ~02:20
Fairly high in the eastern sky
during morning twilight at ~01:40
1-
40o
N
Fairly high at ~02:10
High at ~03:50
High at ~03:30
High during morning twilight at
~03:40
Fairly high in the eastern sky
at ~01:10
1-
Equator
High in moonlight at ~02:00
High at ~04:40
High at ~04:30
High at ~04:30
High in moonlight at ~04:40
2-
30o S
High in moonlight at ~04:40
High at ~04:50
High at ~04:50
High at ~05:00
High in moonlight at ~05:00
2-
This comet begins the month in Triangulum at magnitude 9.8. Look
for a 7.5' coma. It should fade rapidly, moving into Auriga by month's end.
FINDER CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
Nights Visible
55o
N
Low in the western sky during
evening twilight at ~20:50
Low in the western sky during
evening twilight at ~21:10
Low in the western sky during
evening twilight at ~21:30
Not visible
Not visible
1-23, 28-
40o
N
Low in the western sky during
evening twilight at ~20:00
Low in the western sky during
evening twilight at ~20:10
Low in the western sky during
evening twilight at ~20:20
Fairly high in the western sky
during evening twilight at ~20:20
Low in the western sky during
evening twilight at ~20:30
1-24, 27-
Equator
Not visible
Not visible
Not visible
Not visible
Not visible
28-
30o S
Not visible
Not visible
Not visible
Not visible
Not visible
This comet begins the month in Pegasus at magnitude 12.2. Look
for a 3.5' coma. It should fade by about 0.8 magnitudes by month's end. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
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
Low in the eastern sky during
morning twilight at ~04:50
Low in the eastern sky during
morning twilight at ~04:50
Fairly high in the eastern sky
during morning twilight at ~04:50
11-
30o S
Not visible
Not visible
Not visible
Low in the eastern sky during
morning twilight at ~05:10
Low in the eastern sky during
morning twilight at ~05:10
20-25, 29-
This comet begins the month in Eridanus at magnitude 13.2. Look
for a 4' coma. It should fade by about 1.2 magnitudes by month's end. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
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 ~19:20
Fairly high in the western sky
during evening twilight at ~19:10
Low in the western sky during
evening twilight at ~19:10
Not visible
Not visible
1-17
30o S
Fairly high at ~19:10
Fairly high in the western sky
at ~19:10
Fairly high in the western sky
during evening twilight at ~19:00
Not visible
Not visible
1-20
This comet begins the month in Hydrus at magnitude 13.7. Look
for a 60" coma. It should fade by about 0.7 magnitudes, moving into
Reticulum by month's end. The best visibility is early in the month as seen from
the southern hemisphere. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
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 at ~19:20
Fairly high at ~19:10
Fairly high in moonlight at
~19:00
Fairly high during evening
twilight at ~18:50
Fairly high at ~18:50
1-
This comet begins the month in Puppis at magnitude 14.6. Look
for a 1' coma. It should remain constant. The best visibility is late in the
month as seen from the southern hemisphere. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
Nights Visible
55o
N
Not visible
Not visible
Not visible
Not visible
Not visible
40o
N
Low in the southern sky during
evening twilight at ~20:00
Low in the southern sky during
evening twilight at ~20:00
Not visible
Not visible
Not visible
1-14
Equator
High at ~19:30
High at ~19:20
High in moonlight at ~19:20
High during evening twilight at
~19:10
High at ~19:20
1-
30o S
High at ~19:30
High at ~19:20
High in moonlight at ~19:20
High during evening twilight at
~18:40
High at ~18:50
1-
This comet begins the month in Pavo at magnitude 14.7. Look for
a 25" coma. It should brighten slowly. The best visibility is late in the
month as seen from the southern hemisphere. FINDER
CHART
Latitude
Visibility April 3
Visibility April 10
Visibility April 17
Visibility April 24
Visibility May 1
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 in the southern sky
during morning twilight at ~04:50
Low in the southern sky at
~04:50
Low in the southern sky at
~04:50
Low in the southern sky during
morning twilight at ~04:40
Low in the southern sky during
morning twilight at ~04:40
1-
30o S
High in moonlight at ~04:50
High at ~04:50
High at ~04:50
High at ~05:00
Fairly high in the southern sky
at ~22:10
1-
Summary Data for This Month's Telescopic Comets
Comet | Constellation |
April 1st |
April 15th |
April 30th |
Observations as of (UT) | |||
Mag | Diam | Mag | Diam | Mag | Diam | |||
C/2020 R4 (ATLAS) | Aquila | 8.9 | 4.7' | 8.4 | 6.8' | 8.8 | 7.2' | 2021 March 26 |
C/2021 D1 (SWAN) | Triangulum | 10.0 | 7.6' | 10.5 | 7.2' | 11.3 | 6.5' | 2021 March 16 |
10P/Tempel | Aquarius | 10.6 | 2.0' | 10.7 | 2.1' | 11.0 | 2.1' | 2021 March 26 |
C/2019 L3 (ATLAS) | Andromeda | 11.6 | 1.5' | 11.6 | 1.5' | 11.5 | 1.5' | 2021 March 16 |
C/2020 S3 (Erasmus) | Pegasus | 12.3 | 3.6' | 12.6 | 3.5' | 12.9 | 3.4' | 2021 January 2 |
C/2020 T2 (Palomar) | Canes Venatici | 12.6 | 1.6' | 12.5 | 1.7' | 12.3 | 1.7' | 2021 March 26 |
7P/Pons-Winnecke | Ophiuchus | 13.1 | 5.4' | 12.6 | 6.0' | 11.9 | 7.1' | 2021 March 28 |
C/2020 J1 (SONEAR) | Scorpius | 13.2 | 30" | 13.1 | 32" | 12.9 | 34" | 2021 March 25 |
C/2021 A4 (NEOWISE) | Eridanus | 13.3 | 3.7' | 13.8 | 3.3' | 14.4 | 2.9' | 2021 March 28 |
246P/NEAT | Sagittarius | 13.5 | 39" | 13.4 | 41" | 13.3 | 44" | 2021 March 20 |
C/2019 N1 (ATLAS) | Hydrus | 13.8 | 59" | 14.0 | 56" | 14.4 | 52" | 2021 March 25 |
C/2017 K2 (PANSTARRS) | Lyra | 14.1 | 26" | 14.0 | 27" | 13.8 | 28" | 2021 April 2 |
88P/Howell | Pisces | 14.3 | 2.9' | 14.6 | 2.8' | 15.0 | 2.8' | 2021 February 22 |
C/2019 T4 (ATLAS) | Puppis | 14.6 | 1.2' | 14.5 | 1.2' | 14.5 | 1.2' | 2021 March 26 |
C/2019 F1 (ATLAS-Africano) | Pavo | 14.7 | 22" | 14.6 | 22" | 14.5 | 23" | 2021 March 26 |
C/2018 N2 (ASASSN) | Draco | 15.1 | 2.1' | 15.1 | 2.0' | 15.3 | 2.0' | 2021 March 30 |
156P/Russell-LINEAR | Auriga | 15.3 | 13" | 15.6 | 12" | 16.1 | 11" | 2021 April 2 |
C/2020 M3 (ATLAS) | Lynx | 15.5 | 2.5' | 15.9 | 2.2' | 16.4 | 2.0' | 2021 March 30 |
29P/Schwassmann-Wachmann | Aries | 15.8 | 24" | 15.8 | 24" | 15.9 | 23" | 2021 April 4 |
C/2021 A2 (NEOWISE) | Auriga | 15.8 | 1.1' | 16.3 | 60" | 16.9 | 52" | 2021 March 31 |
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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