Comet Chasing in December


Comet chasing is the visual observation of telescopic comets.

News


  • C/2018 V1 (Machholz-Fujikawa-Iwamoto) is a new rare visual discovery.  See MPEC 2018-V151 for the discovery details.  It will reach perihelion in early December when it will also pass within 0.7 AU of the earth. This comet exceeds the Bortle limit so it is unlikely to survive perihilion.

  • 46P/Wirtanen will reach perihelion in mid-December, when it will pass within 0.1 AU of the earth and is predicted to reach maximum brightness of magnitude 2.5.

  • 38P/Stephan-Oterma passed perihelion in early November. In mid December this comet will pass within 0.8 AU of the earth. It is predicted to reach maximum brightness of magnitude 6.7 in late November.

  • C/2017 S3 (PANSTARRS) has apparently disintegrated during perihelion passage. Juan Jose Gonzalez reported visual sightings of the remnant as recently as November 16, but no other observers have confirmed.    During an outburst in July it brightened by ~3 magnitudes, making it a visually observable object. On July 20 it was a binocular object at magnitude 7.3. 

  • 64P/Swift-Gehrels passed perihelion in early November, when it will also pass within 0.4 AU of the earth and is predicted to reach maximum brightness of magnitude 9.7.

  • C/2018 L2 (ATLAS) will reach perihelion in early December. It is predicted to reach maximum brightness of magnitude 9.3 in mid December. 

  • 21P/Giacobini-Zinner passed perihelion in early September. Also in early September this comet will pass within 0.4 AU of the earth, when it is currently predicted to reach maximum brightness of magnitude 7.

  • 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/2018 N1 (NEOWISE) is a recent discovery (July 5).  Michael Mattiazzo reported that it is bright enough to be observed visually, and Paul Camilleri confirmed that is was magnitude 11.4 on July 9. This comet will passed perihelion in early August. In late July passed within 0.3 AU of the earth. Peak brightness of magnitude 9.3 was on July 27.

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

  • C/2016 R2 (PANSTARRS) passed perihelion in early May. 

  • C/2016 N6 (PANSTARRS) passed perihelion in mid July. 

  • 48P/Johnson passed perihelion in mid August.

  • 37P/Forbes passed perihelion in early May.

  • C/2015 O1 (PANSTARRS) is past perihelion, which occurred in mid February 2018.

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 December


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

46P/Wirtanen: An evening comet visible to the naked eye
This comet begins the month in Cetus at magnitude 4.7. Look for a 120' coma. It should remain constant, moving into Lynx by month's end.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N Low in the southern sky at ~22:00 Fairly high at ~22:00 High at ~00:00 High in moonlight at ~23:10 High at ~00:10 1-
40o N Fairly high at ~21:50 High at ~22:00 High at ~00:10 High in moonlight at ~23:10 High at ~00:10 1-
Equator High at ~21:50 High at ~22:00 High at ~00:30 High in moonlight at ~23:00 Fairly high at ~00:10 1-
30o S High at ~21:50 High at ~21:50 Fairly high in the northern sky at ~00:40 Low in the northern sky in moonlight at ~23:00 Very low in the northern sky at ~00:10 1-

38P/Stephan-Oterma: A morning comet visible in binoculars
This comet begins the month in Cancer at magnitude 6.7. Look for a 11' coma. It should fade by about 0.8 magnitudes, moving into Lynx by month's end.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N High at ~01:40 High at ~03:10 High at ~02:50 High in moonlight at ~02:30 High at ~00:50 1-
40o N High at ~01:40 High at ~03:10 High at ~02:50 High in moonlight at ~02:30 High at ~00:40 1-
Equator High at ~01:50 High at ~03:10 High at ~02:50 High in moonlight at ~02:40 High at ~00:40 1-
30o S Fairly high in the northern sky at ~01:50 Fairly high in the northern sky at ~03:00 Fairly high in the northern sky at ~02:50 Fairly high in the northern sky in moonlight at ~02:30 Low in the northern sky at ~00:30 1-

C/2018 V1 (Machholz-Fujikawa-Iwamoto): An evening comet visible in small telescopes
This comet begins the month in Ophiuchus at magnitude 5.3. Look for a 6' coma. It should fade rapidly, moving into Sagittarius by month's end.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N Very low in the western sky during evening twilight at ~17:20 Very low in the western sky during evening twilight at ~17:30 Very low in the western sky during evening twilight at ~17:10 Not visible Not visible 1-25
40o N Very low in the western sky during evening twilight at ~17:50 Very low in the western sky during evening twilight at ~18:00 Very low in the western sky during evening twilight at ~17:50 Very low in the western sky during evening twilight at ~17:40 Not visible 1-28
Equator Not visible Very low in the western sky during evening twilight at ~18:50 Very low in the western sky during evening twilight at ~19:00 Very low in the western sky during evening twilight at ~18:50 Not visible 2-28, 30-30
30o S Not visible Not visible Very low in the western sky during evening twilight at ~19:40 Not visible Not visible 7-25

C/2018 L2 (ATLAS): A northern hemisphere evening comet visible in small telescopes
This comet begins the month in Ophiuchus at magnitude 8.9. Look for a 6.5' coma. It should remain constant, moving into Hercules by month's end.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N Low in the western sky during evening twilight at ~17:50 Low in the western sky during evening twilight at ~17:40 Low in the western sky during evening twilight at ~17:30 Fairly high in the western sky during evening twilight at ~17:20 Low in the western sky during evening twilight at ~17:50 1-
40o N Low in the western sky during evening twilight at ~18:10 Low in the western sky during evening twilight at ~18:10 Low in the western sky during evening twilight at ~18:00 Low in the western sky during evening twilight at ~17:50 Low in the western sky during evening twilight at ~18:10 1-
Equator Not visible Not visible Not visible Not visible Not visible 1-4, 8-8
30o S Not visible Not visible Not visible Not visible Not visible  

64P/Swift-Gehrels: An evening comet visible in small telescopes
This comet begins the month in Triangulum at magnitude 9.0. Look for a 8.5' coma. It should fade rapidly, moving into Aries by month's end.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N High at ~21:00 High at ~20:50 High at ~00:00 High in moonlight at ~20:40 High at ~20:20 1-
40o N High at ~21:00 High at ~20:50 High at ~00:10 High in moonlight at ~20:40 High at ~20:20 1-
Equator High at ~21:00 High at ~20:50 Fairly high in the western sky at ~00:30 High in moonlight at ~20:30 High at ~20:20 1-
30o S Fairly high in the northern sky at ~21:00 Fairly high in the northern sky at ~20:50 Fairly high in the northern sky in moonlight at ~20:40 Fairly high in the northern sky during evening twilight at ~20:30 Fairly high in the northern sky at ~20:50 1-

C/2016 R2 (PANSTARRS): A northern hemisphere morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Bootes at magnitude 10.3. Look for a 7' coma. It should fade slowly.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N High in moonlight at ~05:50 High at ~05:50 High at ~05:50 High during morning twilight at ~06:20 High in moonlight at ~06:10 1-
40o N High in moonlight at ~05:30 High at ~05:30 High at ~05:30 High during morning twilight at ~05:50 High during morning twilight at ~05:40 1-
Equator Very low in the eastern sky during morning twilight at ~04:50 Low in the eastern sky during morning twilight at ~04:40 Low in the eastern sky during morning twilight at ~04:40 Fairly high in the eastern sky during morning twilight at ~05:00 Fairly high in the eastern sky during morning twilight at ~04:50 1-
30o S Not visible Not visible Not visible Not visible Not visible  

C/2016 M1 (PANSTARRS): A southern hemisphere morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Apus at magnitude 10.5. Look for a 3.5' coma. It should fade slowly, moving into Octans by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 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 31-
30o S Fairly high in the southern sky at ~01:50 Fairly high in the southern sky at ~03:10 Fairly high in the southern sky at ~03:10 Fairly high in the southern sky during morning twilight at ~03:20 Fairly high in the southern sky at ~20:50 1-

21P/Giacobini-Zinner: A morning comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Puppis at magnitude 11.3. Look for a 8' coma. It should fade rapidly, moving into Columba by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Low in the southern sky at ~01:40 Low in the southern sky at ~01:50 Low in the southern sky at ~01:10 Low in the southern sky in moonlight at ~00:30 Low in the southern sky at ~23:50 1-
Equator High at ~01:50 High at ~01:50 High at ~01:10 High in moonlight at ~00:30 High at ~23:50 1-
30o S High at ~01:50 High at ~01:50 High at ~01:10 High in moonlight at ~00:30 High at ~23:50 1-

C/2016 N6 (PANSTARRS): A morning comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Hydra at magnitude 12.6. Look for a 2' coma. It should fade slowly, moving into Canis Major by month's end.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N Fairly high in the southern sky in moonlight at ~03:50 Fairly high in the southern sky at ~03:00 Fairly high in the southern sky at ~02:20 Low in the southern sky in moonlight at ~01:40 Low in the southern sky at ~00:50 1-
40o N Fairly high at ~01:40 Fairly high at ~03:00 Fairly high at ~02:20 Fairly high in moonlight at ~01:40 Fairly high at ~00:40 1-
Equator High at ~01:50 High at ~03:00 High at ~02:20 High in moonlight at ~01:40 High at ~00:40 1-
30o S High at ~01:50 High at ~02:50 High at ~02:20 High in moonlight at ~01:40 High at ~00:30 1-

29P/Schwassmann-Wachmann: An evening comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Aquarius at magnitude 13.3. Look for a 1' coma. It should fade slowly, moving into Pisces by month's end.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N Fairly high at ~18:10 Fairly high at ~18:00 Fairly high during evening twilight at ~17:40 Fairly high during evening twilight at ~17:50 Fairly high at ~18:00 1-
40o N High at ~18:30 High at ~18:20 High during evening twilight at ~18:10 High during evening twilight at ~18:10 High at ~18:30 1-
Equator High at ~19:10 High at ~19:20 High during evening twilight at ~19:10 High during evening twilight at ~19:10 High at ~19:20 1-
30o S High at ~20:20 High during evening twilight at ~20:30 Fairly high during evening twilight at ~20:20 Fairly high during evening twilight at ~20:20 Fairly high in the western sky during evening twilight at ~20:30 1-

C/2015 O1 (PANSTARRS): A morning comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Ursa Major at magnitude 13.5. Look for a 45" coma. It should remain constant.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N High in moonlight at ~05:40 High at ~05:40 High at ~05:40 High in moonlight at ~05:00 High at ~00:50 1-
40o N High in moonlight at ~05:20 High at ~05:20 High at ~05:20 High in moonlight at ~05:00 High at ~00:40 1-
Equator Fairly high during morning twilight at ~04:30 High at ~04:30 High at ~04:30 High during morning twilight at ~04:40 High in moonlight at ~04:40 1-
30o S Very low in the northern sky during morning twilight at ~03:40 Very low in the northern sky during morning twilight at ~03:30 Low in the northern sky during morning twilight at ~03:30 Low in the northern sky during morning twilight at ~03:50 Low in the northern sky during morning twilight at ~03:40 1-

364P/PANSTARRS: An evening comet visible in a 14-inch (36 cm) telescope
This comet begins the month in Aquarius at magnitude 13.6. Look for a 1.5' coma. It should fade by about 0.9 magnitudes, moving into Pisces by month's end.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N Fairly high in the southern sky at ~19:10 Fairly high in the southern sky at ~18:50 Fairly high in the southern sky during evening twilight at ~17:30 Fairly high in moonlight at ~18:40 Fairly high at ~18:10 1-
40o N High at ~19:10 High at ~18:50 High during evening twilight at ~18:00 High in moonlight at ~18:50 High at ~18:30 1-
Equator High at ~19:20 High at ~19:20 High during evening twilight at ~19:00 High in moonlight at ~19:20 High at ~19:30 1-
30o S High at ~20:30 High at ~20:30 High during evening twilight at ~20:10 High during evening twilight at ~20:20 High during evening twilight at ~20:40 1-

37P/Forbes: An evening comet visible in very large telescopes
This comet begins the month in Pisces at magnitude 13.4. Look for a 3.5' coma. It should fade by about 0.9 magnitudes by month's end.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N High at ~18:40 High at ~18:20 High in moonlight at ~17:50 High in moonlight at ~18:20 High at ~18:10 1-
40o N High at ~18:40 High at ~18:30 High in moonlight at ~18:10 High in moonlight at ~18:40 High at ~18:30 1-
Equator High at ~19:20 High at ~19:20 High during evening twilight at ~19:10 High during evening twilight at ~19:20 High at ~19:30 1-
30o S High at ~20:30 High at ~20:30 Fairly high during evening twilight at ~20:20 Fairly high during evening twilight at ~20:20 Fairly high in the western sky during evening twilight at ~20:40 1-

C/2017 M4 (ATLAS): A northern hemisphere morning comet visible in very large telescopes
This comet begins the month in Ophiuchus at magnitude 14.0. Look for a 1' coma. It should remain constant.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N Not visible Not visible Very low in the eastern sky during morning twilight at ~06:40 Very low in the eastern sky during morning twilight at ~06:50 Very low in the eastern sky during morning twilight at ~06:30 15-
40o N Not visible Not visible Not visible Very low in the eastern sky during morning twilight at ~06:10 Very low in the eastern sky during morning twilight at ~06:00 18-
Equator Not visible Not visible Not visible Not visible Very low in the eastern sky during morning twilight at ~05:00 28-
30o S Not visible Not visible Not visible Not visible Not visible  

C/2018 N2 (ASASSN): An evening comet visible in very large telescopes
This comet begins the month in Phoenix at magnitude 14.3. Look for a 1' coma. It should remain constant, moving into Sculptor by month's end. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility December 1 Visibility December 8 Visibility December 15 Visibility December 22 Visibility December 29 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Very low in the southern sky at ~20:40 Low in the southern sky at ~20:10 Low in the southern sky in moonlight at ~19:30 Low in the southern sky in moonlight at ~19:10 Low in the southern sky at ~18:40 1-
Equator High at ~20:40 High at ~20:10 High in moonlight at ~19:30 High in moonlight at ~20:00 High at ~19:30 1-
30o S High at ~20:50 High at ~20:40 Fairly high in the western sky at ~00:40 High in moonlight at ~20:40 High at ~20:50 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

December 1st

December 15th

December 31st

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
46P/Wirtanen Cetus 4.7 80.0' 3.7 123.5' 4.7 81.9' 2018 December 1
C/2018 V1 (Machholz-Fujikawa-Iwamoto) Ophiuchus 5.3 7.7' 7.5 4.5' 10.3 3.2' 2018 November 16
C/2018 L2 (ATLAS) Ophiuchus 8.9 6.2' 8.9 6.3' 9.0 6.4' 2018 November 4
64P/Swift-Gehrels Triangulum 9.0 8.5' 9.7 7.4' 10.8 6.1' 2018 December 1
C/2016 R2 (PANSTARRS) Bootes 10.3 7.0' 10.4 7.0' 10.6 7.0' 2018 November 16
C/2016 M1 (PANSTARRS) Apus 10.5 3.4' 10.7 3.4' 10.9 3.4' 2018 November 29
38P/Stephan-Oterma Cancer 11.1 1.7' 11.3 1.7' 11.9 1.7' 2018 November 14
C/2018 N1 (NEOWISE) Libra 11.9 3.0' 12.2 3.0' 12.5 3.1' 2018 October 4
21P/Giacobini-Zinner Puppis 12.6 1.7' 13.4 1.5' 14.2 1.4' 2018 October 21
C/2016 N6 (PANSTARRS) Hydra 12.6 2.0' 12.6 2.1' 12.7 2.1' 2018 November 29
29P/Schwassmann-Wachmann Aquarius 13.3 1.2' 13.4 1.2' 13.5 1.1' 2018 November 26
37P/Forbes Pisces 13.4 3.7' 13.8 3.3' 14.2 2.9' 2018 September 19
C/2015 O1 (PANSTARRS) Ursa Major 13.5 44" 13.5 46" 13.5 48" 2018 November 14
364P/PANSTARRS Aquarius 13.6 1.6' 14.0 1.4' 14.5 1.2' 2018 October 4
78P/Gehrels Aquarius 13.9 1.0' 13.8 58" 13.8 55" 2018 November 30
48P/Johnson Aquarius 13.9 49" 14.3 45" 14.6 40" 2018 November 30
C/2017 M4 (ATLAS) Ophiuchus 14.0 1.0' 14.0 1.0' 13.9 1.0' 2018 November 14
C/2018 N2 (ASASSN) Phoenix 14.3 1.1' 14.2 1.0' 14.2 1.0' 2018 November 30
60P/Tsuchinshan Leo 15.2 16" 15.0 17" 14.8 19" 2018 November 14
C/2017 T2 (PANSTARRS) Eridanus 15.6 20" 15.5 20" 15.4 20" 2018 November 14
*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