Comet Chasing in April


Comet chasing is the visual observation of telescopic comets.

News


  • C/2018 Y1 (Iwamoto) passed perihelion in early February. 

  • C/2018 A6 (Gibbs) will reach perihelion in mid July. It is currently predicted to reach maximum brightness of magnitude 13.5 in late June.

  • 78P/Gehrels will reach perihelion in early April. It is currently predicted to reach maximum brightness of magnitude 11.5 in mid March.

  • C/2017 T2 (PANSTARRS) will reach perihelion in early May 2020. It is currently predicted to reach naked eye visibility in mid May 2020.

  • 46P/Wirtanen passed perihelion in mid-December, when it also passed within 0.1 AU of the earth. It should continue to fade rapidly.

  • C/2017 M4 (ATLAS) passed perhleion in mid January. It is predicted to reach maximum brightness of magnitude 13 in early May.

  • 123P/West-Hartley passed perihelion in early February.

  • C/2018 N2 (ASASSN) will reach perihelion in mid November 2019. It is currently predicted to reach maximum brightness of magnitude 11.2 in late October.

  • 38P/Stephan-Oterma passed perihelion in early November. 

  • C/2018 L2 (ATLAS) passed perihelion in early December. It should fade slowly.

  • 64P/Swift-Gehrels passed perihelion in early November, when it passed within 0.4 AU of the earth.

  • 21P/Giacobini-Zinner passed perihelion in early September. Also in early September this comet passed within 0.4 AU of the earth.

  • 29P/Schwassmann-Wachmann This comet has outbursts, resulting in a brightening of 0.5 - 1.0 magnitudes, which occur roughly every 59 days, typically taking 5-10 days to subside. But 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 will next reach perihelion in early March 2019. But 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. 

  • C/2016 M1 (PANSTARRS) passed perihelion in early August. Maximum brightness of magnitude 8 occurred in late July. 

  • C/2017 S3 (PANSTARRS) disintegrated during perihelion passage.

Comet Visibility in the Eyepiece

This page uses code developed for SkyTools 3 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 April


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

C/2018 Y1 (Iwamoto): An evening comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Perseus at magnitude 10.5. Look for a 3' coma. It should fade by about 1.5 magnitudes by month's end.  FINDER CHART
Latitude Visibility March 30 Visibility April 6 Visibility April 13 Visibility April 20 Visibility April 27 Nights Visible
55o N Fairly high at ~20:50 Fairly high during evening twilight at ~21:00 Fairly high in the western sky during evening twilight at ~21:00 Fairly high in the western sky during evening twilight at ~21:00 Low in the western sky during evening twilight at ~21:50 1-
40o N High at ~20:00 Fairly high at ~20:10 Fairly high during evening twilight at ~20:00 Fairly high in the western sky during evening twilight at ~20:00 Low in the western sky during evening twilight at ~20:30 1-
Equator Fairly high at ~19:20 Fairly high in the western sky at ~19:20 Fairly high in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~19:10 1-
30o S Low in the northern sky during evening twilight at ~19:10 Very low in the northern sky during evening twilight at ~19:00 Very low in the northern sky during evening twilight at ~18:40 Not visible Not visible 1-21

123P/West-Hartley: An evening comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Leo Minor at magnitude 12.8. Look for a 1' coma. It should fade by about 0.7 magnitudes, moving into Leo by month's end.  FINDER CHART
Latitude Visibility March 30 Visibility April 6 Visibility April 13 Visibility April 20 Visibility April 27 Nights Visible
55o N High at ~22:30 High at ~22:00 High in moonlight at ~21:30 High during evening twilight at ~20:40 High during evening twilight at ~22:20 1-
40o N High at ~22:30 High at ~22:00 Fairly high in the western sky at ~02:30 High during evening twilight at ~20:00 High at ~20:50 1-
Equator High at ~22:30 High at ~22:00 Fairly high in the western sky at ~01:20 High at ~19:10 High at ~20:40 1-
30o S Fairly high at ~22:30 Fairly high at ~22:00 Low in the northern sky at ~00:40 Fairly high in the northern sky during evening twilight at ~18:40 Fairly high at ~20:40 1-

C/2018 A6 (Gibbs): A southern hemisphere evening comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Carina at magnitude 13.4. Look for a 25" coma. It should remain constant. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility March 30 Visibility April 6 Visibility April 13 Visibility April 20 Visibility April 27 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 ~19:40 Fairly high at ~19:20 Fairly high during evening twilight at ~19:10 Fairly high at ~19:10 Fairly high in the southern sky at ~19:10 1-
30o S High at ~19:40 High at ~19:30 Fairly high in the southern sky at ~00:40 High during evening twilight at ~18:40 High at ~19:00 1-

C/2017 T2 (PANSTARRS): An evening comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Cetus at magnitude 10.6. Look for a 3.5' coma. It should brighten slowly, moving into Taurus by month's end.  FINDER CHART
Latitude Visibility March 30 Visibility April 6 Visibility April 13 Visibility April 20 Visibility April 27 Nights Visible
55o N Very low in the western sky during evening twilight at ~20:20 Very low in the western sky during evening twilight at ~20:10 Not visible Not visible Not visible 1-12
40o N Low in the western sky during evening twilight at ~19:50 Very low in the western sky during evening twilight at ~19:50 Very low in the western sky during evening twilight at ~19:40 Not visible Not visible 1-20
Equator Fairly high in the western sky at ~19:20 Low in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~19:00 Very low in the western sky during evening twilight at ~19:00 Very low in the western sky during evening twilight at ~18:50 1-
30o S Low in the western sky during evening twilight at ~19:20 Low in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~18:50 Very low in the western sky during evening twilight at ~18:40 Not visible 1-

C/2017 M4 (ATLAS): A morning comet visible in an 18-inch (46 cm) telescope
This comet begins the month in Ophiuchus at magnitude 13.7. Look for a 1' coma. It should brighten slowly, moving into Scorpius by month's end. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility March 30 Visibility April 6 Visibility April 13 Visibility April 20 Visibility April 27 Nights Visible
55o N Very low in the southern sky during morning twilight at ~03:50 Very low in the southern sky during morning twilight at ~03:30 Not visible Not visible Not visible 1-9
40o N Low in the southern sky at ~03:40 Low in the southern sky at ~03:50 Low in the southern sky at ~03:30 Low in the southern sky in moonlight at ~03:00 Low in the southern sky at ~02:10 1-
Equator High at ~02:30 High at ~04:10 High at ~03:40 High in moonlight at ~03:10 High at ~01:10 1-
30o S High in moonlight at ~04:40 High at ~04:10 High at ~03:40 High in moonlight at ~03:10 High at ~00:30 1-

64P/Swift-Gehrels: An evening comet visible in very large telescopes
This comet begins the month in Gemini at magnitude 13.1. Look for a 3' coma. It should fade rapidly.  FINDER CHART
Latitude Visibility March 30 Visibility April 6 Visibility April 13 Visibility April 20 Visibility April 27 Nights Visible
55o N High at ~20:50 Fairly high at ~21:10 Fairly high during evening twilight at ~21:00 Fairly high during evening twilight at ~21:00 Fairly high in the western sky during evening twilight at ~22:00 1-
40o N High at ~20:00 High at ~20:10 High during evening twilight at ~20:00 High during evening twilight at ~20:00 Fairly high at ~20:40 1-
Equator High at ~19:20 High at ~19:20 High during evening twilight at ~19:10 High at ~19:10 High at ~19:20 1-
30o S Fairly high at ~19:20 Fairly high at ~19:10 Fairly high during evening twilight at ~18:50 Fairly high during evening twilight at ~18:40 Fairly high in the northern sky at ~18:50 1-

C/2018 L2 (ATLAS): A far-northern morning comet visible in very large telescopes
This comet begins the month in Andromeda at magnitude 13.3. Look for a 2' coma. It should fade by about 0.7 magnitudes by month's end.  FINDER CHART
Latitude Visibility March 30 Visibility April 6 Visibility April 13 Visibility April 20 Visibility April 27 Nights Visible
55o N Fairly high in the northern sky during morning twilight at ~03:30 Fairly high in the northern sky during morning twilight at ~03:00 Fairly high in the northern sky during morning twilight at ~03:00 Fairly high in the northern sky during morning twilight at ~02:50 Low in the northern sky during morning twilight at ~01:50 1-
40o N Low in the eastern sky during morning twilight at ~04:20 Low in the eastern sky during morning twilight at ~04:00 Low in the northern sky during morning twilight at ~03:50 Low in the eastern sky during morning twilight at ~04:00 Low in the northern sky during morning twilight at ~03:30 1-
Equator Not visible Not visible Not visible Not visible Not visible  
30o S Not visible Not visible Not visible Not visible Not visible  

78P/Gehrels: A far-northern evening comet visible in very large telescopes
This comet begins the month in Aries at magnitude 13.9. Look for a 2.5' coma. It should fade slowly.  FINDER CHART
Latitude Visibility March 30 Visibility April 6 Visibility April 13 Visibility April 20 Visibility April 27 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Very low in the western sky during evening twilight at ~19:30 Not visible Not visible Not visible Not visible 1-1
Equator Very low in the western sky during evening twilight at ~19:00 Not visible Not visible Not visible Not visible  
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

April 1st

April 15th

April 30th

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
C/2018 Y1 (Iwamoto) Perseus 10.5 3.0' 11.3 2.4' 12.0 2.1' 2019 April 1
C/2017 T2 (PANSTARRS) Cetus 10.6 3.5' 10.5 3.5' 10.4 3.5' 2019 March 24
123P/West-Hartley Leo Minor 12.5 2.5' 12.8 2.3' 13.2 2.1' 2019 April 1
64P/Swift-Gehrels Gemini 13.1 2.8' 14.0 2.5' 14.9 2.2' 2019 February 25
C/2018 L2 (ATLAS) Andromeda 13.3 2.2' 13.6 2.1' 13.9 2.0' 2019 February 27
C/2018 A6 (Gibbs) Carina 13.4 24" 13.4 24" 13.4 23" 2019 March 3
60P/Tsuchinshan Leo 13.5 1.2' 14.0 1.1' 14.5 55" 2019 March 30
46P/Wirtanen Leo Minor 13.6 2.2' 14.5 1.8' 15.3 1.5' 2019 April 1
C/2017 M4 (ATLAS) Ophiuchus 13.7 53" 13.6 57" 13.5 1.0' 2019 March 13
78P/Gehrels Aries 13.8 1.1' 13.9 1.1' 13.9 1.1' 2019 February 24
C/2016 M1 (PANSTARRS) Dorado 14.5 1.2' 14.7 1.2' 15.0 1.1' 2019 March 4
C/2015 O1 (PANSTARRS) Lynx 15.1 2.1' 15.3 2.0' 15.5 1.8' 2019 March 21
38P/Stephan-Oterma Lynx 15.2 41" 16.1 36" 17.0 31" 2019 February 23
240P/NEAT Ursa Major 15.3 28" 15.6 26" 15.9 24" 2019 March 12
C/2018 A3 (ATLAS) Camelopardalis 15.4 26" 15.6 25" 15.8 23" 2019 January 21
C/2016 R2 (PANSTARRS) Hercules 15.8 1.1' 15.9 1.1' 16.1 1.0' 2019 March 22
C/2016 N6 (PANSTARRS) Lepus 16.0 22" 16.2 20" 16.5 19" 2019 February 27
*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 comet observing
 

Links

Skyhound's Guide to Comets
Skyhound's Guide to Finding Comets
BAA Comet Section
Weekly Information About Bright Comets
Cometography