Comet Chasing in April


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

News


February offers an excitring new discovery and three comets visible in a six-inch telescope.
  • 2021 D1 (SWAN) was discovered on SWAN images obtained by the SOHO solar observing spacecraft in late February. It is past perihelion, which occurred in late February.  

  • 2020 T2 (Palomar) will reach perihelion in mid July. It is currently predicted to reach maximum brightness of magnitude 12.2 in late June. 

  • 2020 J1 (SONEAR) will reach perihelion in mid April. It is currently predicted to reach maximum brightness of magnitude 13 in mid May.

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

  • 141P/Machholz was reported to be in outburst on March 5 (up to 3 magnitudes). Other reports suggested that it may have been disintegrating. As of March 16 it had faded to magnitude 15.6. This comet passed perihelion on December 16. In mid January 2021 is passed within 0.5 AU of the earth. Discovered in 1994, this comet has many known separate fragments, at least one dating back to that time. A total of at least 8 have been observed at various apparitions. In December 2020 Michael Jäger reported three fragments. On or near January 1, 2020 the main part of the comet had an outburst of 2 magnitudes and it is this part that is currently visually observable. 

  • 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/2020 R4 (Atlas) will reach perihelion in early March. On March 1, this comet will pass within 0.5 AU of the earth. It t is currently predicted to reach a maximum brightness of magnitude 6 in mid April. 

  • 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) will reach perihelion in mid-March. It should fade slightly going into 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 will next reach perihelion in late February 2021. It is currently predicted to reach maximum brightness of magnitude 13.5 in late June of 20

  • 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
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-

C/2019 L3 (ATLAS): A northern hemisphere evening comet visible in an 8-inch (20 cm) telescope
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  

C/2020 T2 (Palomar): An evening comet visible in an 8-inch (20 cm) telescope
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-

C/2020 J1 (SONEAR): A morning comet visible in an 8-inch (20 cm) telescope
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-

10P/Tempel: A southern hemisphere morning comet visible in a 10-inch (25 cm) telescope
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-

246P/NEAT: A morning comet visible in a 12.5-inch (32 cm) telescope
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-

C/2017 K2 (PANSTARRS): A morning comet visible in a 12.5-inch (32 cm) telescope
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-

7P/Pons-Winnecke: A morning comet visible in an 18-inch (46 cm) telescope
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-

C/2021 D1 (SWAN): A northern hemisphere evening comet visible in very large telescopes
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  

C/2020 S3 (Erasmus): A southern hemisphere morning comet visible in very large telescopes
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-

C/2021 A4 (NEOWISE): A southern hemisphere evening comet visible in very large telescopes
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

C/2019 N1 (ATLAS): A southern hemisphere evening comet visible in very large telescopes
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-

C/2019 T4 (ATLAS): An evening comet visible in very large telescopes
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-

C/2019 F1 (ATLAS-Africano): A southern hemisphere morning comet visible in very large telescopes
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


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

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
*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