Comet Chasing in October


Comet chasing is the visual observation of telescopic comets.

News


  • 38P/Stephan-Oterma will next reach 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.

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

  • 21P/Giacobini-Zinner reached 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 is reported to have had a ~3 magnitude outburst on September 21, and has now faded. Typically, it has primary 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/2017 S3 (PANSTARRS) has faded since its outburst on July 2.  During the outburst it brightened by ~3 magnitudes, making it a visually observable object. On July 20 it was a binocular object at magnitude 7.3. This comet passed perihelion in mid August. It may not have survive perihelion passage because it was past the Bortle limit.

  • 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/2017 T3 (ATLAS) passed perihelion in mid July.

  • 66P/du Toit passed perihelion in mid 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 October


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

21P/Giacobini-Zinner: A morning comet visible in binoculars
This comet begins the month in Monoceros at magnitude 8.2. Look for a 2.5' coma. It should fade rapidly, moving into Canis Major by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Fairly high during morning twilight at ~04:20 Fairly high in the southern sky at ~04:10 Low in the southern sky at ~04:30 Low in the southern sky during morning twilight at ~04:40 Not visible 1-
40o N High during morning twilight at ~04:30 Fairly high at ~04:30 Fairly high at ~04:30 Fairly high in the southern sky at ~04:40 Fairly high in the southern sky during morning twilight at ~04:50 1-
Equator High during morning twilight at ~04:40 High at ~04:20 High at ~04:30 High at ~04:20 High during morning twilight at ~04:30 1-
30o S High during morning twilight at ~04:30 High at ~04:00 High at ~03:50 High at ~03:40 High during morning twilight at ~03:50 1-

38P/Stephan-Oterma: A morning comet visible in binoculars
This comet begins the month in Orion at magnitude 9.4. Look for a 8' coma. It should brighten by about 1.1 magnitudes, moving into Gemini by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N High during morning twilight at ~04:10 High at ~04:00 High at ~04:10 High at ~04:20 High in moonlight at ~04:50 1-
40o N High during morning twilight at ~04:30 High at ~04:20 High at ~04:30 High at ~04:30 High in moonlight at ~04:50 1-
Equator High during morning twilight at ~04:40 High at ~04:20 High at ~04:20 High at ~04:20 High during morning twilight at ~04:30 1-
30o S High during morning twilight at ~04:30 High at ~04:00 High at ~03:50 High at ~03:50 High during morning twilight at ~04:00 1-

46P/Wirtanen: An evening comet visible in small telescopes
This comet begins the month in Fornax at magnitude 11.3. Look for a 5' coma. It should brighten rapidly. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Very low in the southern sky in moonlight at ~01:20 Very low in the southern sky at ~00:50 Very low in the southern sky at ~00:30 Not visible Not visible 1-
40o N Fairly high in the southern sky in moonlight at ~01:30 Fairly high in the southern sky at ~00:50 Fairly high in the southern sky at ~00:30 Very low in the southern sky at ~02:40 Low in the southern sky in moonlight at ~23:40 1-
Equator Fairly high at ~21:40 High at ~00:50 High at ~00:30 Fairly high at ~03:10 Fairly high at ~20:30 1-
30o S High at ~22:20 High at ~00:50 High at ~00:30 High at ~03:30 High at ~21:20 1-

C/2016 M1 (PANSTARRS): A southern hemisphere evening comet visible in small telescopes
This comet begins the month in Centaurus at magnitude 10.2. Look for a 3' coma. It should fade slowly, moving into Circinus by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 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 Very low in the southern sky during evening twilight at ~18:50 Very low in the southern sky during evening twilight at ~18:40 Not visible Not visible Not visible 1-17
30o S Fairly high in the southern sky at ~19:20 Fairly high in the southern sky at ~19:30 Fairly high in the southern sky during evening twilight at ~19:30 Low in the southern sky during morning twilight at ~04:00 Fairly high in the southern sky during evening twilight at ~19:40 1-

64P/Swift-Gehrels: An evening comet visible in small telescopes
This comet begins the month in Andromeda at magnitude 11.6. Look for a 1.5' coma. It should brighten by about 0.7 magnitudes by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N High at ~20:00 High at ~23:30 High at ~23:00 High at ~02:20 High during evening twilight at ~18:30 1-
40o N High at ~20:40 High at ~23:30 High at ~23:00 High at ~02:40 High at ~19:20 1-
Equator High at ~21:40 High at ~23:30 High at ~23:00 Low in the western sky at ~03:10 High at ~20:30 1-
30o S Fairly high in the northern sky at ~22:20 Fairly high in the northern sky at ~23:30 Fairly high in the northern sky at ~23:00 Fairly high in the northern sky in moonlight at ~22:40 Fairly high in the northern sky at ~21:20 1-

29P/Schwassmann-Wachmann: An evening comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Pisces at magnitude 11.4. Look for a 1.5' coma. It should fade slowly, moving into Aquarius by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Fairly high in the southern sky at ~20:00 Fairly high at ~21:50 Fairly high at ~21:20 Fairly high in moonlight at ~20:30 Fairly high in the southern sky during evening twilight at ~18:30 1-
40o N High at ~20:40 High at ~21:50 High at ~21:20 High in moonlight at ~20:30 High at ~19:20 1-
Equator High at ~21:40 High at ~21:50 High at ~21:40 High in moonlight at ~20:30 High at ~20:20 1-
30o S High at ~22:20 High at ~21:50 High at ~22:30 High in moonlight at ~20:30 High at ~20:20 1-

364P/PANSTARRS: An evening comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Cetus at magnitude 12.0. Look for a 3' coma. It should fade by about 1.5 magnitudes, moving into Aquarius by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Low in the southern sky in moonlight at ~23:40 Low in the southern sky at ~22:50 Low in the southern sky at ~22:20 Low in the southern sky in moonlight at ~21:50 Low in the southern sky during evening twilight at ~18:30 1-
40o N Low in the southern sky at ~20:40 Fairly high in the southern sky at ~22:50 Fairly high at ~22:20 Fairly high in moonlight at ~21:40 Fairly high in the southern sky at ~19:20 1-
Equator High at ~21:40 High at ~22:50 High at ~22:20 High in moonlight at ~21:40 High at ~20:30 1-
30o S High at ~22:20 High at ~22:50 High at ~22:30 High in moonlight at ~21:40 High at ~21:20 1-

C/2016 N6 (PANSTARRS): A morning comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Cancer at magnitude 12.3. Look for a 1' coma. It should brighten slowly, moving into Hydra by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Fairly high in the eastern sky during morning twilight at ~04:20 Fairly high in the eastern sky during morning twilight at ~04:20 Fairly high during morning twilight at ~04:30 Fairly high at ~04:40 Fairly high during morning twilight at ~05:10 1-
40o N Fairly high during morning twilight at ~04:40 Fairly high at ~04:30 Fairly high at ~04:40 High at ~04:40 High during morning twilight at ~05:00 1-
Equator Fairly high during morning twilight at ~04:50 Fairly high at ~04:30 High at ~04:30 High at ~04:30 High during morning twilight at ~04:40 1-
30o S Fairly high in the eastern sky during morning twilight at ~04:40 Fairly high in the eastern sky during morning twilight at ~04:10 Fairly high in the eastern sky during morning twilight at ~04:00 Fairly high during morning twilight at ~03:50 High during morning twilight at ~04:00 1-

48P/Johnson: An evening comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Pisces Austrinus at magnitude 12.6. Look for a 1' coma. It should fade by about 0.7 magnitudes by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Very low in the southern sky in moonlight at ~22:00 Very low in the southern sky at ~21:30 Very low in the southern sky at ~21:00 Very low in the southern sky in moonlight at ~20:40 Very low in the southern sky during evening twilight at ~18:30 1-
40o N Low in the southern sky at ~20:40 Fairly high in the southern sky at ~21:30 Fairly high in the southern sky at ~21:00 Fairly high in the southern sky in moonlight at ~20:40 Fairly high in the southern sky at ~19:20 1-
Equator High at ~21:40 High at ~21:30 High at ~21:40 High in moonlight at ~20:30 High at ~20:20 1-
30o S High at ~21:50 High at ~21:30 High at ~22:30 High in moonlight at ~20:30 High at ~20:20 1-

C/2016 R2 (PANSTARRS): A far-northern morning comet visible in a 14-inch (36 cm) telescope
This comet begins the month in Canes Venatici at magnitude 12.7. Look for a 1' coma. It should fade slowly.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Fairly high in the northern sky at ~19:40 Fairly high in the eastern sky at ~04:10 Fairly high in the eastern sky at ~04:20 Fairly high at ~04:40 Fairly high in the western sky during evening twilight at ~18:30 1-
40o N Low in the northern sky during evening twilight at ~19:10 Low in the northern sky during morning twilight at ~04:30 Fairly high in the eastern sky during morning twilight at ~04:40 Fairly high in the eastern sky during morning twilight at ~04:50 Low in the northern sky during evening twilight at ~18:30 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: An evening comet visible in a 14-inch (36 cm) telescope
This comet begins the month in Aquarius at magnitude 13.5. Look for a 55" coma. It should brighten slowly, moving into Capricornus by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Fairly high in the southern sky at ~20:00 Fairly high in the southern sky at ~20:20 Fairly high in the southern sky at ~19:50 Fairly high in the southern sky in moonlight at ~19:00 Fairly high in the southern sky during evening twilight at ~18:30 1-
40o N High at ~20:40 High at ~20:20 High at ~20:30 High in moonlight at ~19:10 High at ~19:10 1-
Equator High at ~20:50 High at ~20:20 High at ~21:40 High in moonlight at ~19:10 High at ~19:10 1-
30o S High at ~20:50 High at ~20:20 High in moonlight at ~19:50 High during evening twilight at ~19:30 High at ~19:50 1-

C/2015 O1 (PANSTARRS): A northern hemisphere morning comet visible in a 16-inch (41 cm) telescope
This comet begins the month in Ursa Major at magnitude 13.9. Look for a 25" coma. It should remain constant.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Low in the northern sky during evening twilight at ~19:30 Fairly high in the eastern sky during morning twilight at ~04:20 Fairly high in the eastern sky during morning twilight at ~04:30 Fairly high at ~04:40 High during morning twilight at ~05:10 1-
40o N 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 ~04:40 Fairly high in the eastern sky during morning twilight at ~04:50 Fairly high during morning twilight at ~05:10 1-
Equator Not visible Not visible Very low in the eastern sky during morning twilight at ~04:50 Very low in the eastern sky during morning twilight at ~04:40 Low in the eastern sky during morning twilight at ~04:50 10-
30o S Not visible Not visible Not visible Not visible Not visible

C/2018 N2 (ASASSN): An evening comet visible in an 18-inch (46 cm) telescope
This comet begins the month in Eridanus at magnitude 13.9. Look for a 1' coma. It should brighten slowly, moving into Phoenix by month's end. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Not visible Very low in the southern sky at ~01:30 Very low in the southern sky at ~01:00 Not visible Not visible 1-18, 29-
Equator Low in the southern sky at ~21:40 High at ~01:30 High at ~01:00 Fairly high in the southern sky at ~03:10 Fairly high in the southern sky at ~20:30 1-
30o S High at ~22:20 High at ~01:30 High at ~01:00 High at ~03:30 High at ~21:20 1-

37P/Forbes: An evening comet visible in very large telescopes
This comet begins the month in Pisces at magnitude 11.4. Look for a 6.5' coma. It should fade by about 1.0 magnitudes by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Fairly high at ~20:00 High at ~22:00 High at ~21:30 Very low in the western sky at ~02:20 Fairly high during evening twilight at ~18:30 1-
40o N High at ~20:40 High at ~22:00 High at ~21:30 High in moonlight at ~20:40 High at ~19:20 1-
Equator High at ~21:40 High at ~22:00 High at ~21:40 High in moonlight at ~20:40 High at ~20:30 1-
30o S High at ~22:20 High at ~22:00 High at ~22:30 High in moonlight at ~20:50 High at ~20:30 1-

66P/du Toit: An evening comet visible in very large telescopes
This comet begins the month in Cetus at magnitude 12.7. Look for a 4' coma. It should fade by about 1.1 magnitudes, moving into Aquarius by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Very low in the eastern sky at ~20:00 Fairly high in the southern sky at ~23:10 Fairly high in the southern sky at ~22:40 Very low in the western sky at ~02:20 Low in the eastern sky during evening twilight at ~18:30 1-
40o N Fairly high in the eastern sky at ~20:40 High at ~23:10 High at ~22:40 Low in the western sky at ~02:40 Fairly high at ~19:20 1-
Equator High at ~21:40 High at ~23:10 High at ~22:40 Low in the western sky at ~03:10 High at ~20:30 1-
30o S High at ~22:20 High at ~23:10 High at ~22:40 Very low in the western sky at ~03:30 High at ~21:20 1-

C/2018 L2 (ATLAS): An evening comet visible in very large telescopes
This comet begins the month in Libra at magnitude 13.7. Look for a 60" coma. It should brighten slowly, moving into Serpens Caput by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Very low in the western sky during evening twilight at ~19:20 Very low in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~18:50 Low in the western sky during evening twilight at ~18:20 Low in the western sky during evening twilight at ~18:30 1-
40o N Low in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~18:50 Low in the western sky during evening twilight at ~18:30 Low in the western sky during evening twilight at ~18:30 1-
Equator Fairly high in the western sky at ~19:00 Fairly high in the western sky during evening twilight at ~19:00 Fairly high in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~18:40 Low in the western sky during evening twilight at ~18:50 1-
30o S Fairly high in the western sky during evening twilight at ~19:20 Low in the western sky during evening twilight at ~19:20 Low in the western sky during evening twilight at ~19:20 Low in the western sky during evening twilight at ~19:10 Very low in the western sky during evening twilight at ~19:20 1-28, 31-

C/2017 M4 (ATLAS): An evening comet visible in very large telescopes
This comet begins the month in Hercules at magnitude 14.1. Look for a 50" coma. It should remain constant, moving into Ophiuchus by month's end.  FINDER CHART
Latitude Visibility September 29 Visibility October 6 Visibility October 13 Visibility October 20 Visibility October 27 Nights Visible
55o N Fairly high in the western sky during evening twilight at ~19:40 Fairly high in the western sky during evening twilight at ~19:20 Fairly high in the western sky during evening twilight at ~19:00 Fairly high in the western sky during evening twilight at ~18:30 Low in the western sky during evening twilight at ~18:30 1-
40o N Fairly high at ~19:20 Fairly high at ~19:10 Fairly high in the western sky during evening twilight at ~18:50 Fairly high in the western sky during evening twilight at ~18:30 Low in the western sky during evening twilight at ~18:30 1-
Equator Fairly high at ~19:10 Fairly high at ~19:00 Fairly high in the western sky during evening twilight at ~19:00 Fairly high in the western sky during evening twilight at ~18:50 Low in the western sky during evening twilight at ~19:00 1-
30o S Fairly high in the western sky during evening twilight at ~19:20 Fairly high in the western sky during evening twilight at ~19:20 Low in the western sky during evening twilight at ~19:20 Low in the western sky during evening twilight at ~19:20 Very low in the western sky during evening twilight at ~19:30 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

October 1st

October 15th

October 31st

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
21P/Giacobini-Zinner Monoceros 8.3 2.8' 9.0 2.3' 10.0 1.9' 2018 September 24
38P/Stephan-Oterma Orion 9.3 6.7' 8.8 7.5' 8.3 8.5' 2018 September 19
C/2016 M1 (PANSTARRS) Centaurus 10.2 2.8' 10.4 2.7' 10.6 2.6' 2018 October 1
46P/Wirtanen Fornax 11.2 3.0' 10.2 3.8' 9.0 5.1' 2018 October 2
37P/Forbes Pisces 11.4 6.4' 11.8 5.7' 12.4 4.9' 2018 September 19
29P/Schwassmann-Wachmann Pisces 11.4 1.6' 11.5 1.6' 11.5 1.5' 2018 September 30
64P/Swift-Gehrels Andromeda 11.6 1.3' 11.1 1.4' 10.9 1.5' 2018 October 1
364P/PANSTARRS Cetus 12.0 2.8' 12.7 2.2' 13.5 1.7' 2018 September 19
C/2016 N6 (PANSTARRS) Cancer 12.3 1.1' 12.2 1.1' 12.1 1.2' 2018 September 20
48P/Johnson Pisces Austrinus 12.6 1.1' 12.9 1.0' 13.3 55" 2018 October 1
C/2016 R2 (PANSTARRS) Canes Venatici 12.7 1.0' 12.8 1.0' 12.9 1.0' 2018 September 9
78P/Gehrels Aquarius 13.5 1.0' 13.4 59" 13.3 55" 2018 September 30
C/2018 L2 (ATLAS) Libra 13.7 59" 13.6 59" 13.5 59" 2018 September 6
C/2018 N2 (ASASSN) Eridanus 13.9 1.1' 13.7 1.1' 13.6 1.1' 2018 September 19
C/2015 O1 (PANSTARRS) Ursa Major 13.9 25" 13.9 26" 13.9 26" 2018 August 12
C/2017 M4 (ATLAS) Hercules 14.1 50" 14.1 48" 14.2 46" 2018 September 30
C/2018 N1 (NEOWISE) Libra 14.2 1.3' 14.7 1.1' 15.3 1.0' 2018 September 8
C/2017 T3 (ATLAS) Hydra 14.5 59" 15.2 54" 15.9 48" 2018 August 29
C/2017 S3 (PANSTARRS) Coma Berenices 15.4 1.7' 16.3 1.6' 17.2 1.5' 2018 August 2
*In solar conjunction and generally not visible

For information about specific comets see Gary W. Kronk's Cometography 

Join the Comet Chasing discussion group 

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