Comet Chasing in September


Comet chasing is the visual observation of telescopic comets.

News


  • 29P/Schwassmann-Wachmann is reported to have had a ~3 magnitude outburst on September 21, now as bright as magnitude 10.5. 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. 

  • 21P/Giacobini-Zinner will reach 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.

  • 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.

  • 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 September


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 Auriga at magnitude 7.1. Look for a 3.5' coma. It should fade slowly, moving into Monoceros by month's end.  FINDER CHART

Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Low in the northern sky at ~21:30 High at ~03:00 High at ~03:20 Fairly high at ~03:40 Fairly high during morning twilight at ~04:20 1-
40o N High during morning twilight at ~04:00 High at ~03:50 High at ~04:00 High at ~04:10 High during morning twilight at ~04:30 1-
Equator Fairly high during morning twilight at ~04:50 High at ~04:40 High at ~04:40 High at ~04:30 High during morning twilight at ~04:40 1-
30o S Low in the northern sky during morning twilight at ~05:10 Fairly high in the northern sky at ~04:50 Fairly high in the northern sky at ~04:30 High during morning twilight at ~04:40 High during morning twilight at ~04:30 1-

38P/Stephan-Oterma: A morning comet visible in binoculars
This comet begins the month in Taurus at magnitude 9.8. Look for a 6.5' coma. It should brighten rapidly, moving into Orion by month's end.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Fairly high during morning twilight at ~03:20 Fairly high at ~03:10 Fairly high at ~03:20 High at ~03:40 High during morning twilight at ~04:10 1-
40o N High during morning twilight at ~04:10 High at ~04:00 High at ~04:00 High at ~04:10 High during morning twilight at ~04:30 1-
Equator High during morning twilight at ~04:50 High at ~04:40 High at ~04:30 High at ~04:30 High during morning twilight at ~04:40 1-
30o S High during morning twilight at ~05:00 High at ~04:40 High at ~04:30 High during morning twilight at ~05:00 High during morning twilight at ~04:30 1-

C/2016 M1 (PANSTARRS): A southern hemisphere evening comet visible in small telescopes
This comet begins the month in Centaurus at magnitude 9.9. Look for a 3' coma. It should fade slowly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 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 Low in the southern sky during evening twilight at ~19:10 Low in the southern sky during evening twilight at ~19:10 Low in the southern sky during evening twilight at ~19:00 Low in the southern sky during evening twilight at ~18:50 Very low in the southern sky during evening twilight at ~18:50 1-
30o S High at ~19:10 High at ~19:10 Fairly high during evening twilight at ~19:10 Fairly high during evening twilight at ~19:00 Fairly high in the southern sky at ~19:20 1-

64P/Swift-Gehrels: An evening comet visible in small telescopes
This comet begins the month in Pisces at magnitude 12.2. Look for a 2' coma. It should brighten rapidly, moving into Andromeda by month's end.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Fairly high at ~21:30 High at ~01:10 High at ~00:50 High at ~03:20 High at ~20:00 1-
40o N High at ~22:00 High at ~01:10 High at ~00:50 High at ~03:50 High at ~20:40 1-
Equator High at ~22:50 High at ~01:10 High at ~00:40 Fairly high in the western sky at ~04:40 High at ~21:40 1-
30o S Fairly high at ~23:30 Fairly high at ~01:10 Fairly high at ~00:50 Fairly high in moonlight at ~00:20 Fairly high in the northern sky at ~22:20 1-

C/2018 N1 (NEOWISE): An evening comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Libra at magnitude 10.3. Look for a 5' coma. It should fade rapidly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Very low in the western sky during evening twilight at ~20:30 Very low in the western sky during evening twilight at ~20:10 Very low in the western sky during evening twilight at ~19:50 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-
40o N Low in the western sky during evening twilight at ~20:00 Low in the western sky during evening twilight at ~19:50 Low in the western sky during evening twilight at ~19:30 Low in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~19:10 1-
Equator High at ~19:20 High at ~19:10 Fairly high during evening twilight at ~19:00 Fairly high during evening twilight at ~18:50 Fairly high in the western sky during evening twilight at ~19:00 1-
30o S High at ~19:10 High at ~19:10 Fairly high during evening twilight at ~19:10 Fairly high in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~19:20 1-

C/2016 R2 (PANSTARRS): A far-northern evening comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Ursa Major at magnitude 10.5. Look for a 7' coma. It should fade slowly, moving into Canes Venatici by month's end.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Fairly high in the northern sky at ~21:10 Fairly high in the northern sky at ~20:50 Fairly high in the northern sky at ~03:20 Fairly high in the northern sky at ~03:40 Fairly high in the northern sky at ~19:40 1-
40o N Low in the northern sky during evening twilight at ~20:00 Low in the northern sky during evening twilight at ~19:50 Low in the northern sky during morning twilight at ~04:10 Low in the northern sky during morning twilight at ~04:20 Low in the northern sky during evening twilight at ~19:10 1-
Equator Not visible Not visible Not visible Not visible Not visible  
30o S Not visible Not visible Not visible Not visible Not visible  

29P/Schwassmann-Wachmann: An evening comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Pisces at magnitude 10.7. Look for a 5' coma. It should remain constant.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Fairly high in the eastern sky at ~21:30 Fairly high at ~23:50 Fairly high at ~23:20 Low in the western sky at ~03:20 Fairly high in the southern sky at ~20:00 1-
40o N Fairly high at ~22:00 High at ~23:50 High at ~23:20 Low in the western sky at ~03:50 High at ~20:40 1-
Equator High at ~22:50 High at ~23:50 High at ~23:20 High in moonlight at ~22:40 High at ~21:40 1-
30o S High at ~23:30 High at ~23:50 High at ~23:50 High in moonlight at ~22:40 High at ~22:20 1-

C/2016 N6 (PANSTARRS): A morning comet visible in a 14-inch (36 cm) telescope
This comet begins the month in Cancer at magnitude 11.9. Look for a 3' coma. It should remain constant.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Very low in the eastern sky during morning twilight at ~03:30 Low in the eastern sky during morning twilight at ~03:30 Low in the eastern sky during morning twilight at ~03:40 Low in the eastern sky during morning twilight at ~03:50 Fairly high in the eastern sky during morning twilight at ~04:20 1-
40o N Low in the eastern sky during morning twilight at ~04:10 Low in the eastern sky during morning twilight at ~04:10 Fairly high in the eastern sky during morning twilight at ~04:10 Fairly high in the eastern sky during morning twilight at ~04:20 Fairly high during morning twilight at ~04:40 1-
Equator Low in the eastern sky during morning twilight at ~05:00 Low in the eastern sky during morning twilight at ~04:50 Fairly high in the eastern sky during morning twilight at ~04:40 Fairly high in the eastern sky at ~04:40 Fairly high during morning twilight at ~04:50 1-
30o S Very low in the eastern sky during morning twilight at ~05:20 Very low in the eastern sky during morning twilight at ~05:00 Low in the eastern sky during morning twilight at ~04:50 Low in the eastern sky during morning twilight at ~04:50 Fairly high in the eastern sky during morning twilight at ~04:30 1-

37P/Forbes: A morning comet visible in a 16-inch (41 cm) telescope
This comet begins the month in Pisces at magnitude 10.7. Look for a 6' coma. It should fade by about 0.7 magnitudes by month's end.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Fairly high in the eastern sky at ~21:30 High at ~00:10 High at ~23:30 Low in the western sky at ~03:20 Fairly high at ~20:00 1-
40o N High at ~22:00 High at ~00:10 High at ~23:30 Low in the western sky at ~03:50 High at ~20:40 1-
Equator High at ~22:50 High at ~00:10 High at ~23:30 High in moonlight at ~22:50 High at ~21:40 1-
30o S High at ~23:30 High at ~00:10 High at ~23:50 High in moonlight at ~22:50 High at ~22:20 1-

66P/du Toit: A morning comet visible in very large telescopes
This comet begins the month in Cetus at magnitude 11.8. Look for a 5' coma. It should fade by about 0.9 magnitudes by month's end.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Fairly high in the southern sky in moonlight at ~02:20 Fairly high in the southern sky at ~01:40 Fairly high in the southern sky at ~01:00 Low in the western sky at ~03:30 Very low in the eastern sky at ~20:00 1-
40o N Fairly high in moonlight at ~02:30 Fairly high at ~01:40 Fairly high at ~01:00 Low in the western sky at ~03:50 Fairly high in the eastern sky at ~20:40 1-
Equator Fairly high at ~22:50 High at ~01:40 High at ~01:00 Fairly high in the western sky at ~04:30 High at ~21:40 1-
30o S High at ~23:30 High at ~01:40 High at ~01:00 High in moonlight at ~00:30 High at ~22:20 1-

C/2017 T3 (ATLAS): A southern hemisphere evening comet visible in very large telescopes
This comet begins the month in Hydra at magnitude 12.5. Look for a 1.5' coma. It should fade rapidly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 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  
30o S 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 ~19:00 Low in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~19:10 1-

48P/Johnson: An evening comet visible in very large telescopes
This comet begins the month in Pisces Austrinus at magnitude 12.7. Look for a 3' coma. It should fade slowly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Very low in the southern sky in moonlight at ~00:00 Very low in the southern sky at ~23:20 Very low in the southern sky at ~22:50 Not visible Very low in the southern sky in moonlight at ~22:00 1-19, 28-
40o N Low in the southern sky at ~22:00 Fairly high in the southern sky at ~23:20 Fairly high in the southern sky at ~22:50 Fairly high in the southern sky in moonlight at ~22:20 Low in the southern sky at ~20:40 1-
Equator High at ~22:50 High at ~23:20 High at ~23:00 High in moonlight at ~22:20 High at ~21:40 1-
30o S High at ~23:30 High at ~23:20 High at ~23:50 High in moonlight at ~22:20 High at ~21:50 1-

C/2015 O1 (PANSTARRS): A far-northern evening comet visible in very large telescopes
This comet begins the month in Ursa Major at magnitude 13.4. Look for a 1' coma. It should fade slowly.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Low in the western sky during evening twilight at ~21:00 Low in the western sky during evening twilight at ~20:40 Low in the northern sky during morning twilight at ~03:40 Low in the eastern sky during morning twilight at ~03:50 Low in the northern sky during evening twilight at ~19:30 1-
40o N Low in the western sky during evening twilight at ~20:00 Low in the western sky during evening twilight at ~19:50 Low in the western sky during evening twilight at ~19:30 Very low in the eastern sky during morning twilight at ~04:30 Low in the eastern sky during morning twilight at ~04:40 1-
Equator Not visible Not visible Not visible Not visible Not visible  
30o S Not visible Not visible Not visible Not visible Not visible  

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. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Very low in the western sky during evening twilight at ~20:20 Very low in the western sky during evening twilight at ~20:00 Very low in the western sky during evening twilight at ~19:50 Very low in the western sky during evening twilight at ~19:20 Very low in the western sky during evening twilight at ~19:20 1-
40o N Low in the western sky during evening twilight at ~20:00 Low in the western sky during evening twilight at ~19:50 Low in the western sky during evening twilight at ~19:30 Low in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~19:10 1-
Equator Fairly high at ~19:20 Fairly high at ~19:10 Fairly high during evening twilight at ~19:00 Fairly high during evening twilight at ~18:50 Fairly high in the western sky at ~19:00 1-
30o S High at ~19:10 Fairly high at ~19:10 Fairly high during evening twilight at ~19:10 Fairly high in the western sky during evening twilight at ~19:00 Fairly high in the western sky during evening twilight at ~19:20 1-

78P/Gehrels: An evening comet visible in very large telescopes
This comet begins the month in Aquarius at magnitude 14.4. Look for a 1' coma. It should brighten slowly.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Fairly high in the southern sky at ~21:30 Fairly high in the southern sky at ~22:20 Fairly high in the southern sky at ~21:50 Fairly high in the southern sky in moonlight at ~20:50 Fairly high in the southern sky at ~20:00 1-
40o N High at ~22:00 High at ~22:20 High at ~22:00 High in moonlight at ~21:00 High at ~20:40 1-
Equator High at ~22:50 High at ~22:20 High at ~23:00 High in moonlight at ~21:00 High at ~20:50 1-
30o S High at ~22:50 High at ~22:20 High at ~23:50 High in moonlight at ~21:10 High at ~20:50 1-

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 40" coma. It should remain constant.  FINDER CHART
Latitude Visibility September 1 Visibility September 8 Visibility September 15 Visibility September 22 Visibility September 29 Nights Visible
55o N Fairly high during evening twilight at ~21:10 Fairly high during evening twilight at ~20:50 Fairly high in the western sky at ~21:10 Fairly high during evening twilight at ~19:40 Fairly high in the western sky during evening twilight at ~19:40 1-
40o N High at ~20:10 High at ~20:00 High during evening twilight at ~19:40 High during evening twilight at ~19:10 Fairly high at ~19:20 1-
Equator High at ~19:20 High at ~19:20 High during evening twilight at ~19:10 High during evening twilight at ~19:00 Fairly high at ~19:10 1-
30o S Fairly high at ~19:10 Fairly high at ~19:10 Fairly high during evening twilight at ~19:10 Fairly high during evening twilight at ~19:00 Fairly high in the western sky during evening twilight at ~19:20 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

September 1st

September 15th

September 30th

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
21P/Giacobini-Zinner Auriga 7.1 3.3' 7.0 3.4' 7.6 3.0' 2018 August 23
38P/Stephan-Oterma Taurus 9.8 5.5' 8.9 6.2' 8.1 7.1' 2018 August 20
C/2016 M1 (PANSTARRS) Centaurus 9.9 2.9' 10.1 2.6' 10.4 2.4' 2018 August 29
C/2018 N1 (NEOWISE) Libra 10.3 5.2' 11.1 3.9' 11.9 3.2' 2018 August 15
C/2016 R2 (PANSTARRS) Ursa Major 10.5 7.0' 10.6 7.0' 10.7 7.0' 2018 August 15
29P/Schwassmann-Wachmann Pisces 12 5.1' 10.5 4' 10.4? 4.0'? 2018 September 23
37P/Forbes Pisces 10.7 5.9' 11.0 5.6' 11.4 5.0' 2018 August 20
C/2017 S3 (PANSTARRS) Leo 11.2 2.3' 13.6 1.9' 15.2 1.7' 2018 August 2
66P/du Toit Cetus 11.8 4.9' 12.2 4.6' 12.6 4.1' 2018 August 20
C/2016 N6 (PANSTARRS) Cancer 11.9 2.7' 11.9 2.8' 11.9 2.9' 2018 July 9
64P/Swift-Gehrels Pisces 12.2 1.3' 11.3 1.6' 10.4 1.8' 2018 August 20
C/2017 T3 (ATLAS) Hydra 12.5 1.4' 13.5 1.2' 14.4 1.0' 2018 August 29
48P/Johnson Pisces Austrinus 12.7 2.9' 12.9 2.8' 13.1 2.5' 2018 August 29
C/2015 O1 (PANSTARRS) Ursa Major 13.4 1.2' 13.5 1.2' 13.5 1.2' 2018 July 14
C/2018 L2 (ATLAS) Libra 13.7 58" 13.6 56" 13.4 55" 2018 August 11
C/2017 M4 (ATLAS) Hercules 14.1 41" 14.1 39" 14.2 38" 2018 July 30
364P/PANSTARRS Sculptor 14.3 29" 15.1 23" 15.9 17" 2018 August 18
78P/Gehrels Aquarius 14.4 1.1' 14.2 1.1' 14.1 1.0' 2018 August 8
C/2017 B3 (LINEAR) Musca 15.0 11" 15.0 11" 15.0 11" 2018 June 18
C/2018 N2 (ASASSN) Eridanus 15.3 14" 15.1 14" 15.0 15" 2018 July 14
C/2015 V2 (Johnson) Eridanus 15.4 58" 15.6 57" 15.8 55" 2018 July 15

*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