Comet Chasing in May


Comet chasing is the visual observation of telescopic comets.

News


This month brings the slimmest pickings for telescopic comets in recent memory.
  • C/2017 M4 (ATLAS) passed perhleion in mid January. It is predicted to reach maximum brightness of magnitude 13 in early May.

  • 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 passed perihelion in early April.

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

  • 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.

  • P/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. 

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 May


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

C/2017 M4 (ATLAS): A morning comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Scorpius at magnitude 12.5. Look for a 50" coma. It should fade slowly, moving into Lupus by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility May 4 Visibility May 11 Visibility May 18 Visibility May 25 Visibility June 1 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Low in the southern sky at ~01:30 Low in the southern sky at ~01:20 Very low in the southern sky in moonlight at ~00:00 Very low in the southern sky at ~23:10 Very low in the southern sky at ~22:30 1-
Equator High at ~01:30 High at ~00:50 High in moonlight at ~00:00 High at ~23:10 High at ~22:30 1-
30o S High at ~01:30 High at ~00:50 High in moonlight at ~00:00 High at ~23:10 High at ~22:30 1-

C/2016 M1 (PANSTARRS): A southern hemisphere evening comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Columba at magnitude 12.6. Look for a 1.5' coma. It should fade slowly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility May 4 Visibility May 11 Visibility May 18 Visibility May 25 Visibility June 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 western sky during evening twilight at ~19:00 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 ~18:50 Not visible 1-29
30o S Fairly high at ~18:50 Fairly high during evening twilight at ~18:30 Fairly high during evening twilight at ~18:20 Fairly high in the western sky during evening twilight at ~18:30 Fairly high in the western sky during evening twilight at ~18:30 1-

C/2018 A6 (Gibbs): A southern hemisphere evening comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Carina at magnitude 13.5. Look for a 40" coma. It should remain constant. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility May 4 Visibility May 11 Visibility May 18 Visibility May 25 Visibility June 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 at ~19:10 Fairly high in the southern sky during evening twilight at ~19:10 Fairly high in the southern sky during evening twilight at ~19:00 Low in the southern sky during evening twilight at ~19:10 Low in the southern sky during evening twilight at ~19:10 1-
30o S High at ~18:50 High during evening twilight at ~18:40 High during evening twilight at ~18:30 High at ~18:40 High at ~18:40 1-

123P/West-Hartley: An evening comet visible in a 16-inch (41 cm) telescope
This comet begins the month in Leo at magnitude 13.8. Look for a 1' coma. It should fade by about 0.8 magnitudes by month's end.  FINDER CHART
Latitude Visibility May 4 Visibility May 11 Visibility May 18 Visibility May 25 Visibility June 1 Nights Visible
55o N High during evening twilight at ~22:40 High during evening twilight at ~22:40 Fairly high during evening twilight at ~22:30 Fairly high in the western sky during evening twilight at ~23:30 Fairly high in the western sky during evening twilight at ~23:30 1-
40o N High at ~20:50 High during evening twilight at ~20:50 High during evening twilight at ~20:50 High at ~21:10 High during evening twilight at ~21:20 1-
Equator High at ~20:20 High in moonlight at ~19:50 High in moonlight at ~20:00 High at ~19:30 High at ~19:20 1-
30o S Fairly high at ~20:20 High in moonlight at ~19:50 High in moonlight at ~19:50 High at ~19:10 High at ~18:50 1-

C/2019 D1 (Flewelling): A morning comet visible in very large telescopes
This comet begins the month in Pegasus at magnitude 14.2. Look for a 1' coma. It should remain constant.  FINDER CHART
Latitude Visibility May 4 Visibility May 11 Visibility May 18 Visibility May 25 Visibility June 1 Nights Visible
55o N Fairly high in the eastern sky during morning twilight at ~01:40 Fairly high in the eastern sky during morning twilight at ~01:30 Fairly high in the eastern sky during morning twilight at ~01:30 Fairly high in the eastern sky during morning twilight at ~00:30 Fairly high in the eastern sky during morning twilight at ~00:20 1-
40o N Fairly high at ~03:10 Fairly high at ~03:00 High during morning twilight at ~03:10 Fairly high in the eastern sky at ~00:40 High at ~02:30 1-
Equator High at ~04:40 High at ~04:40 High during morning twilight at ~04:50 High during morning twilight at ~04:40 High at ~04:30 1-
30o S Fairly high at ~05:10 Fairly high at ~05:10 Fairly high during morning twilight at ~05:30 Fairly high in the northern sky during morning twilight at ~05:30 Fairly high in the northern sky at ~05:20 1-

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

May 1st

May 15th

May 31st

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
C/2017 M4 (ATLAS) Scorpius 12.5 51" 12.5 52" 12.7 51" 2019 April 12
C/2016 M1 (PANSTARRS) Columba 12.6 1.5' 12.8 1.4' 13.0 1.4' 2019 April 28
C/2018 A6 (Gibbs) Carina 13.5 39" 13.5 39" 13.5 38" 2019 April 28
123P/West-Hartley Leo 13.8 1.0' 14.2 56" 14.6 50" 2019 May 1
C/2019 D1 (Flewelling) Pegasus 14.2 1.2' 14.2 1.2' 14.2 1.3' 2019 April 23
*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