Comet Chasing in July


Comet chasing is the visual observation of telescopic comets.

News


This month brings the slimmest pickings for telescopic comets in recent memory.
  • C/2017 T2 (PANSTARRS) will reach perihelion in early May 2020. It is currently predicted to reach naked eye visibility in mid May 2020. As of July 1st, it is lost in the sun's glare. It is likely to reappear during July, and it may be fairly bright.

  • C/2018 A6 (Gibbs) will reach perihelion in mid July. It likely reached maximum brightness in late June.

  • P/2008 Y12 (SOHO) has not yet been recovered, even though it was predicted to be approximately magnitude 12 in July.

  • C/2018 W2 (Africano) will reach perihelion in early September. In late September this comet will pass within 0.5 AU of the earth, when it is predicted to reach maximum brightness of magnitude 8.8.

  • C/2018 N2 (ASASSN) will reach perihelion in mid November. It is predicted to reach maximum brightness of magnitude 11.5 in late October.

  • C/2018 R3 (Lemmon) passed perihelion in early June. 

  • C/2019 D1 (Flewelling) passed perihelion in mid May.

  • C/2018 W1 (Catalina) passed perihelion in mid May. It is predicted to reach maximum brightness of magnitude 11.2 in early June.

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

  • 78P/Gehrels passed perihelion in early April.

  • C/2016 M1 (PANSTARRS) is past perihelion, which occurred in early August 2018. It reached maximum brightness of magnitude 8.7 in late July 2018. 

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

  • 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. 

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 July


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

C/2018 W2 (Africano): A northern hemisphere morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Camelopardus at magnitude 12.6. Look for a 55" coma. It should brighten by about 1.1 magnitudes by month's end.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 Nights Visible
55o N Fairly high in the northern sky during morning twilight at ~00:10 Fairly high in the northern sky during morning twilight at ~00:10 Fairly high during morning twilight at ~00:30 Fairly high during morning twilight at ~00:50 Fairly high during morning twilight at ~00:20 1-
40o N Fairly high in the northern sky at ~02:30 Fairly high in the northern sky at ~02:40 Fairly high at ~02:40 Fairly high during morning twilight at ~03:10 Fairly high in moonlight at ~03:00 1-
Equator Very low in the northern sky during morning twilight at ~05:00 Very low in the northern sky during morning twilight at ~04:50 Low in the northern sky during morning twilight at ~04:50 Low in the northern sky during morning twilight at ~05:00 Low in the northern sky during morning twilight at ~04:50 1-
30o S Not visible Not visible Not visible Not visible Not visible  

C/2018 N2 (ASASSN): A morning comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Cetus at magnitude 13.0. Look for a 1.5' coma. It should brighten slowly, moving into Aries by month's end.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 Nights Visible
55o N Not visible Not visible Low in the eastern sky during morning twilight at ~01:30 Low in the eastern sky during morning twilight at ~01:40 Low in the eastern sky during morning twilight at ~01:10 4-
40o N Low in the eastern sky during morning twilight at ~02:50 Low in the eastern sky during morning twilight at ~02:50 Fairly high in the eastern sky during morning twilight at ~02:50 Fairly high during morning twilight at ~03:20 High during morning twilight at ~03:10 1-
Equator Fairly high in moonlight at ~04:40 High at ~04:40 High at ~04:40 High during morning twilight at ~05:00 High in moonlight at ~04:40 1-
30o S Fairly high in moonlight at ~05:30 Fairly high at ~05:30 High at ~05:20 High during morning twilight at ~05:40 High in moonlight at ~05:20 1-

C/2018 W1 (Catalina): A southern hemisphere evening comet visible in a 16-inch (41 cm) telescope
This comet begins the month in Puppis at magnitude 11.9. Look for a 2' coma. It should fade by about 0.6 magnitudes, moving into Antlia by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 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 Not visible Very 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 ~19:10 Very low in the western sky during evening twilight at ~19:10 1-2, 4-
30o S Fairly high in the western sky during evening twilight at ~18:40 Fairly high in the western sky during evening twilight at ~18:40 Fairly high during evening twilight at ~18:30 Fairly high at ~18:50 Fairly high at ~18:50 1-

C/2019 D1 (Flewelling): A morning comet visible in an 18-inch (46 cm) telescope
This comet begins the month in Andromeda at magnitude 13.9. Look for a 40" coma. It should fade slowly.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 Nights Visible
55o N Fairly high during morning twilight at ~00:10 Fairly high during morning twilight at ~00:10 High during morning twilight at ~01:30 High during morning twilight at ~01:00 High during morning twilight at ~00:20 1-
40o N High at ~02:30 High at ~02:30 High at ~02:40 Low in the northern sky at ~21:50 High in moonlight at ~03:00 1-
Equator High in moonlight at ~04:40 High at ~04:40 High at ~04:40 High in moonlight at ~04:50 High in moonlight at ~04:30 1-
30o S Low in the northern sky in moonlight at ~05:20 Low in the northern sky at ~05:20 Low in the northern sky at ~05:10 Low in the northern sky in moonlight at ~04:50 Low in the northern sky in moonlight at ~04:40 1-

C/2018 R3 (Lemmon): A northern hemisphere evening comet visible in very large telescopes
This comet begins the month in Lynx at magnitude 9.6. Look for a 5' coma. It should fade by about 0.9 magnitudes, moving into Cancer by month's end.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 Nights Visible
55o N Low in the northern sky during evening twilight at ~23:50 Very low in the northern sky during evening twilight at ~23:40 Very low in the northern sky during evening twilight at ~22:40 Very low in the northern sky during evening twilight at ~22:10 Not visible 1-23
40o N Low in the northern sky during evening twilight at ~21:20 Very low in the northern sky during evening twilight at ~21:10 Very low in the western sky during evening twilight at ~20:50 Very low in the western sky during evening twilight at ~20:40 Not visible 1-25
Equator Very low in the northern sky during evening twilight at ~19:00 Not visible Not visible Not visible Not visible 1-5, 9-11
30o S Not visible Not visible Not visible Not visible Not visible  

29P/Schwassmann-Wachmann: A morning comet visible in very large telescopes
This comet begins the month in Pisces at magnitude 13.9. Look for a 3' coma. It should brighten slowly.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 27 Nights Visible
55o N Low in the eastern sky during morning twilight at ~00:50 Low in the eastern sky during morning twilight at ~00:40 Fairly high in the eastern sky during morning twilight at ~01:30 Fairly high during morning twilight at ~01:20 Fairly high in the eastern sky during morning twilight at ~00:20 1-
40o N Fairly high during morning twilight at ~02:30 Fairly high at ~02:40 High at ~02:40 High during morning twilight at ~03:10 High in moonlight at ~03:00 1-
Equator High in moonlight at ~04:40 High at ~04:40 High at ~04:40 High during morning twilight at ~04:50 High in moonlight at ~04:40 1-
30o S High in moonlight at ~05:20 High at ~05:20 High at ~05:10 High in moonlight at ~05:10 Fairly high at ~03:10 1-

C/2018 A6 (Gibbs): A southern hemisphere evening comet visible in very large telescopes
This comet begins the month in Carina at magnitude 14.0. Look for a 45" coma. It should remain constant. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 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 Not visible Not visible Not visible Not visible Not visible  
30o S Fairly high in the southern sky during evening twilight at ~18:40 Fairly high in the southern sky during evening twilight at ~18:40 Low in the southern sky during morning twilight at ~05:40 Fairly high in the southern sky during evening twilight at ~18:40 Fairly high in the southern sky during morning twilight at ~05:30 1-

C/2016 M1 (PANSTARRS): A southern hemisphere morning comet visible in very large telescopes
This comet begins the month in Canis Major at magnitude 13.8. Look for a 1' coma. It should fade slowly. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility June 29 Visibility July 6 Visibility July 13 Visibility July 20 Visibility July 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 Not visible Not visible Not visible Not visible Low in the eastern sky during morning twilight at ~05:00 21-
30o S Low in the eastern sky during morning twilight at ~05:40 Low in the eastern sky during morning twilight at ~05:40 Fairly high in the eastern sky during morning twilight at ~05:30 Fairly high in the eastern sky during morning twilight at ~05:40 Fairly high in the eastern sky during morning twilight at ~05:30 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

July 1st

July 15th

July 31st

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
C/2018 R3 (Lemmon) Lynx 9.6 4.9' 10.0 4.6' 10.4 4.3' 2019 June 27
C/2018 W1 (Catalina) Puppis 11.9 2.0' 12.1 1.9' 12.5 1.7' 2019 June 24
C/2018 W2 (Africano) Camelopardalis 12.6 40" 12.1 44" 11.5 52" 2019 June 27
C/2018 N2 (ASASSN) Cetus 13.0 1.4' 12.8 1.5' 12.5 1.6' 2019 July 1
C/2016 M1 (PANSTARRS) Canis Major 13.8 1.2' 14.0 1.2' 14.2 1.2' 2019 June 1
29P/Schwassmann-Wachmann Pisces 13.9 3.0' 13.8 3.1' 13.7 3.2' 2019 June 30
C/2018 A6 (Gibbs) Carina 14.0 44" 14.0 44" 14.0 44" 2019 May 31
C/2017 B3 (LINEAR) Phoenix 14.8 45" 14.7 46" 14.7 47" 2019 June 11
68P/Klemola Ophiuchus 14.8 54" 14.6 55" 14.5 54" 2019 June 30
C/2016 N6 (PANSTARRS) Canis Major 14.9? 2.0'? 15.1? 1.9'? 15.2? 1.9'? 2019 May 8
C/2019 D1 (Flewelling) Andromeda 15.0 1.5' 15.2 1.5' 15.4 1.5' 2019 June 14
260P/McNaught Cetus 15.6 24" 15.1 28" 14.6 32" 2019 July 1
*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