Comet Chasing in December


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. 

  • C/2018 N2 (ASASSN) passed perihelion in mid November. 

  • C/2018 W2 (Africano)  passed perihelion in early September.

  • 260P/McNaught passed perihelion in early September. 

  • 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...

  • C/2018 A6 (Gibbs) passed perihelion in mid July.

  • 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. 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 contuniously.

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

2I/Borisov - the first discovered interstellar comet

Three 10-minute exposures taken with iTelescope T11 at New Mexico Skies on the morning of September 12, 2019 - Greg Crinklaw

Find out more and track the science as it develops here.

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)

C/2017 T2 (PANSTARRS): An evening comet visible in small telescopes
This comet begins the month in Auriga at magnitude 10.3. Look for a 2' coma. It should brighten by about 0.7 magnitudes, moving into Perseus by month's end.  FINDER CHART
Latitude Visibility November 30 Visibility December 7 Visibility December 14 Visibility December 21 Visibility December 28 Nights Visible
55o N High at ~00:20 High at ~03:20 High at ~17:50 High at ~22:00 High at ~21:10 1-
40o N High at ~00:20 High at ~03:00 High at ~19:00 High at ~22:00 High at ~21:10 1-
Equator High at ~00:20 Fairly high in the northern sky at ~02:40 Fairly high at ~20:20 Fairly high at ~22:00 Fairly high at ~21:10 1-
30o S Low in the northern sky at ~00:20 Low in the northern sky in moonlight at ~23:30 Very low in the northern sky at ~21:20 Very low in the northern sky at ~22:00 Very low in the northern sky at ~21:10 1-

C/2018 N2 (ASASSN): An evening comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Andromeda at magnitude 11.4. Look for a 2.5' coma. It should fade slowly.  FINDER CHART
Latitude Visibility November 30 Visibility December 7 Visibility December 14 Visibility December 21 Visibility December 28 Nights Visible
55o N High at ~19:10 Low in the northern sky at ~03:20 High at ~17:50 High at ~18:10 High at ~18:10 1-
40o N High at ~20:10 High in moonlight at ~18:20 High at ~18:30 High at ~18:30 High at ~18:30 1-
Equator High in moonlight at ~19:20 High during evening twilight at ~19:10 High at ~19:20 High at ~19:20 Fairly high in moonlight at ~19:20 1-
30o S Low in the northern sky during evening twilight at ~20:20 Low in the northern sky during evening twilight at ~20:00 Low in the northern sky during evening twilight at ~20:20 Low in the northern sky during evening twilight at ~20:20 Very low in the northern sky during evening twilight at ~20:20 1-

260P/McNaught: An evening comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Andromeda at magnitude 13.2. Look for a 50" coma. It should fade by about 1.2 magnitudes, moving into Perseus by month's end.  FINDER CHART
Latitude Visibility November 30 Visibility December 7 Visibility December 14 Visibility December 21 Visibility December 28 Nights Visible
55o N High at ~21:50 Fairly high at ~03:20 High at ~17:50 High at ~20:40 High at ~20:20 1-
40o N High at ~21:50 Fairly high at ~03:00 High at ~19:00 High at ~20:40 High at ~20:20 1-
Equator High at ~21:50 High in moonlight at ~21:10 High at ~20:20 High at ~20:40 High at ~20:20 1-
30o S Low in the northern sky at ~22:30 Low in the northern sky in moonlight at ~21:20 Low in the northern sky at ~21:00 Low in the northern sky at ~20:40 Low in the northern sky at ~20:40 1-

29P/Schwassmann-Wachmann: An evening comet visible in very large telescopes
This comet begins the month in Pisces at magnitude 12.7. Look for a 6.5' coma. It should fade slowly.  FINDER CHART
Latitude Visibility November 30 Visibility December 7 Visibility December 14 Visibility December 21 Visibility December 28 Nights Visible
55o N High at ~19:50 High in moonlight at ~18:50 High at ~17:50 High at ~18:30 High at ~18:20 1-
40o N High at ~20:10 High in moonlight at ~19:00 High at ~18:50 High at ~18:40 High at ~19:00 1-
Equator High at ~21:30 High in moonlight at ~19:10 High at ~19:20 High at ~19:30 High in moonlight at ~19:30 1-
30o S High in moonlight at ~20:30 High during evening twilight at ~20:10 High at ~20:40 Fairly high at ~20:40 Fairly high at ~20:40 1-

C/2018 W2 (Africano): An evening comet visible in very large telescopes
This comet begins the month in Grus at magnitude 13.7. Look for a 1' coma. It should fade by about 1.2 magnitudes by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility November 30 Visibility December 7 Visibility December 14 Visibility December 21 Visibility December 28 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Very low in the southern sky during evening twilight at ~18:00 Not visible Not visible Not visible Not visible 1-6
Equator Fairly high in moonlight at ~19:10 Fairly high during evening twilight at ~19:00 Fairly high in the southern sky at ~19:20 Fairly high in the southern sky at ~19:20 Fairly high in the southern sky during evening twilight at ~19:20 1-
30o S High in moonlight at ~20:20 High during evening twilight at ~20:20 Fairly high at ~20:40 Fairly high at ~20:40 Fairly high in the western sky at ~20:40 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
C/2017 T2 (PANSTARRS) Auriga 10.4 2.5' 10.0 2.7' 9.7 2.8' 2019 December 1
C/2018 N2 (ASASSN) Andromeda 11.4 2.5' 11.6 2.3' 11.8 2.2' 2019 December 1
260P/McNaught Andromeda 11.7 56" 12.2 49" 12.9 41" 2019 November 19
C/2018 W2 (Africano) Grus 13.7 1.1' 14.3 58" 14.9 51" 2019 November 19
68P/Klemola Capricornus 13.8 3.4' 14.0 3.2' 14.2 3.0' 2019 November 15
29P/Schwassmann-Wachmann Pisces 14.8 53" 14.8 51" 15.0 49" 2019 November 19
C/2018 A6 (Gibbs) Pavo 14.8 26" 15.0 25" 15.1 24" 2019 November 19
C/2017 B3 (LINEAR) Pisces Austrinus 14.9 30" 15.0 29" 15.2 27" 2019 November 19
C/2016 M1 (PANSTARRS) Columba 15.0 24" 15.1 24" 15.2 23" 2019 November 20
101P/Chernykh Aquarius 15.0 23" 15.1 21" 15.3 19" 2019 November 5
2I/Borisov Crater 15.1 48" 15.0 50" 15.0 51" 2019 November 6
C/2018 DO4 (Lemmon) Cetus 15.8 18" 16.2 15" 16.7 13" 2019 November 5
*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