Comet Chasing in August


Comet chasing is the visual observation of telescopic comets.

News


  • 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.

  • 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 reach perihelion in early August. In late July this it will pass 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 will reach perihelion in mid August. It may not survive perihelion passage  because it is currently past the Bortle limit.

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

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

  • 21P/Giacobini-Zinner will next reach perihelion in early September, when it will pass within 0.4 AU of the earth and is predicted to reach maximum brightness of magnitude.

  • C/2016 N6 (PANSTARRS) will reach perihelion in mid July. It is predicted to reach maximum brightness of magnitude 12.3 in late June.

  • 48P/Johnson will next reach perihelion in mid August when it is predicted to reach maximum brightness of magnitude 12.8.

  • 37P/Forbes passed perihelion in early May.

  • C/2017 T3 (ATLAS) will reach 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.

  • 62P/Tsuchinshan was recovered in August. It had not been seen since 2004. It brightened significantly and passed perihelion in late November. It has recently been too close to the sun to be observed.

  • 29P/Schwassmann-Wachmann Primary outbursts, resulting in a brightening of 0.5 - 1.0 magnitudes, occur roughly every 59 days, typically taking 5-10 days to subside. But up to three subsequent outbursts, such as the one ones recently, may occur 5-10 days afterward, each typically smaller than the last, but sometimes they can be even brighter than the first.  

 

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 August


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 Cassiopeia at magnitude 8.8. Look for a 7.5' coma. It should brighten rapidly, moving into Auriga by month's end.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N High during evening twilight at ~23:00 High at ~01:10 High at ~01:40 High during morning twilight at ~02:40 Low in the northern sky at ~21:30 1-
40o N High at ~23:30 High at ~03:10 High at ~03:20 High in moonlight at ~03:40 High during morning twilight at ~04:00 1-
Equator Low in the northern sky at ~00:10 Fairly high in the northern sky at ~04:30 Fairly high in the northern sky at ~04:40 Fairly high in moonlight at ~04:50 Fairly high during morning twilight at ~04:50 1-
30o S Not visible Not visible Not visible Not visible Low in the northern sky during morning twilight at ~05:10 23-

C/2016 M1 (PANSTARRS): A southern hemisphere evening comet visible in binoculars
This comet begins the month in Circinus at magnitude 8.7. Look for a 4.5' coma. It should fade by about 0.6 magnitudes, moving into Centaurus by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 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 Fairly high at ~19:30 Fairly high in the southern sky at ~19:20 Fairly high in the southern sky during evening twilight at ~19:10 Fairly high in the southern sky during evening twilight at ~19:00 Low in the southern sky during evening twilight at ~19:10 1-
30o S High at ~19:10 High at ~19:10 High during evening twilight at ~19:00 High during evening twilight at ~19:00 High at ~19:10 1-

C/2017 S3 (PANSTARRS): A morning comet visible in small telescopes
This comet begins the month in Auriga at magnitude 7.2. Look for a 5.5' coma. It should fade by about 1.4 magnitudes, moving into Leo by month's end.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Very low in the northern sky during morning twilight at ~02:20 Not visible Not visible Not visible Not visible 1-7
40o N Very low in the eastern sky during morning twilight at ~03:40 Not visible Not visible Not visible Not visible 1-8
Equator Very low in the eastern sky during morning twilight at ~05:10 Not visible Not visible Not visible Not visible 1-11
30o S Not visible Not visible Not visible Not visible Not visible 7-15

29P/Schwassmann-Wachmann: A morning comet visible in small telescopes
This comet begins the month in Pisces at magnitude 9.5. Look for a 4.5' coma. It should remain constant.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Fairly high in the eastern sky during evening twilight at ~23:00 Fairly high at ~01:20 Fairly high at ~01:20 Fairly high in moonlight at ~01:20 Fairly high in the eastern sky at ~21:30 1-
40o N Fairly high at ~23:30 High at ~01:50 High at ~01:20 High in moonlight at ~01:00 Fairly high at ~22:00 1-
Equator High at ~00:10 High at ~01:50 High at ~01:20 High in moonlight at ~00:50 High at ~22:50 1-
30o S High at ~00:30 High at ~01:50 High at ~01:20 High in moonlight at ~00:50 High at ~23:30 1-

C/2018 N1 (NEOWISE): An evening comet visible in small telescopes
This comet begins the month in Scorpius at magnitude 9.4. Look for a 6' coma. It should fade rapidly, moving into Libra by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Very low in the southern sky during evening twilight at ~21:50 Very low in the southern sky during evening twilight at ~21:40 Very low in the western sky during evening twilight at ~21:10 Not visible Very low in the western sky during evening twilight at ~20:30 1-
40o N Fairly high in the southern sky at ~21:00 Fairly high in the southern sky during evening twilight at ~20:40 Fairly high in the southern sky during evening twilight at ~20:10 Fairly high in the western sky during evening twilight at ~20:00 Fairly high in the western sky during evening twilight at ~20:00 1-
Equator High at ~20:00 High at ~19:30 High during evening twilight at ~19:10 High during evening twilight at ~19:10 High at ~19:20 1-
30o S High at ~20:00 High at ~19:10 High during evening twilight at ~18:50 High during evening twilight at ~18:50 High at ~19:10 1-

48P/Johnson: A morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Aquarius at magnitude 9.7. Look for a 6.5' coma. It should remain constant, moving into Pisces Austrinus by month's end. The best visibility is mid-month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Low in the southern sky during morning twilight at ~01:40 Low in the southern sky at ~01:20 Low in the southern sky at ~00:50 Very low in the southern sky in moonlight at ~00:20 Very low in the southern sky in moonlight at ~00:00 1-
40o N Low in the southern sky at ~23:30 Fairly high in the southern sky at ~01:20 Fairly high in the southern sky at ~00:50 Fairly high in the southern sky in moonlight at ~00:30 Low in the southern sky at ~22:00 1-
Equator High at ~00:10 High at ~01:20 High at ~00:50 High in moonlight at ~00:30 High at ~22:50 1-
30o S High at ~00:30 High at ~01:20 High at ~01:00 High in moonlight at ~00:30 High at ~23:30 1-

66P/du Toit: A morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Cetus at magnitude 10.2. Look for a 4' coma. It should fade by about 0.6 magnitudes by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Low in the southern sky during morning twilight at ~02:10 Low in the southern sky during morning twilight at ~02:00 Low in the southern sky during morning twilight at ~02:10 Fairly high in the southern sky during morning twilight at ~02:50 Fairly high in the southern sky in moonlight at ~02:20 1-
40o N Fairly high during morning twilight at ~03:20 Fairly high at ~03:20 Fairly high at ~03:20 Fairly high in moonlight at ~03:00 Fairly high in moonlight at ~02:30 1-
Equator Fairly high in the eastern sky at ~00:10 High at ~04:00 High at ~03:30 High in moonlight at ~03:00 Fairly high at ~22:50 1-
30o S Fairly high at ~00:30 High at ~04:00 High at ~03:30 High in moonlight at ~03:00 High at ~23:30 1-

38P/Stephan-Oterma: A morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Taurus at magnitude 13.6. Look for a 10" coma. It should brighten rapidly.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Low in the eastern sky during morning twilight at ~02:20 Low in the eastern sky during morning twilight at ~02:20 Fairly high in the eastern sky during morning twilight at ~02:50 Fairly high in the eastern sky during morning twilight at ~03:10 Fairly high during morning twilight at ~03:20 1-
40o N Fairly high during morning twilight at ~03:30 Fairly high during morning twilight at ~03:40 Fairly high during morning twilight at ~03:40 High during morning twilight at ~04:00 High during morning twilight at ~04:10 1-
Equator High during morning twilight at ~05:00 High during morning twilight at ~05:00 High during morning twilight at ~05:00 High during morning twilight at ~04:50 High during morning twilight at ~04:50 1-
30o S High during morning twilight at ~05:30 High during morning twilight at ~05:20 High during morning twilight at ~05:10 High during morning twilight at ~05:10 High during morning twilight at ~05:00 1-

C/2017 T3 (ATLAS): A southern hemisphere morning comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Puppis at magnitude 9.3. Look for a 2.5' coma. It should fade rapidly, moving into Hydra by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 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 eastern sky during morning twilight at ~05:40 Very low in the eastern sky during morning twilight at ~05:30 Low in the western sky during evening twilight at ~18:40 Low in the western sky during evening twilight at ~18:40 Low in the western sky during evening twilight at ~19:00 1-

364P/PANSTARRS: A morning comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Eridanus at magnitude 12.5. Look for a 45" coma. It should fade by about 1.5 magnitudes, moving into Sculptor by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Not visible Very low in the southern sky during morning twilight at ~03:50 Low in the southern sky during morning twilight at ~03:50 Low in the southern sky in moonlight at ~03:40 Low in the southern sky in moonlight at ~02:50 4-
Equator High during morning twilight at ~04:50 High at ~04:50 High at ~04:40 High in moonlight at ~03:30 Fairly high in the eastern sky at ~22:50 1-
30o S High during morning twilight at ~05:20 High at ~05:10 High at ~04:50 High in moonlight at ~03:30 High at ~23:30 1-

37P/Forbes: A morning comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Pisces at magnitude 10.6. Look for a 5' coma. It should fade slowly.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Fairly high in the eastern sky during evening twilight at ~23:00 Fairly high at ~01:20 High at ~01:30 High in moonlight at ~01:40 Fairly high in the eastern sky at ~21:30 1-
40o N Fairly high at ~23:30 High at ~02:20 High at ~01:50 High in moonlight at ~01:30 High at ~22:00 1-
Equator High at ~00:10 High at ~02:20 High at ~01:50 High in moonlight at ~01:20 High at ~22:50 1-
30o S High at ~00:30 High at ~02:20 High at ~01:50 High in moonlight at ~01:20 High at ~23:30 1-

C/2016 N6 (PANSTARRS): A morning comet visible in very large telescopes
This comet begins the month in Cancer at magnitude 11.9. Look for a 2.5' coma. It should remain constant.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Not visible Not visible Very low in the eastern sky during morning twilight at ~03:10 Very low in the eastern sky during morning twilight at ~03:30 Very low in the eastern sky during morning twilight at ~03:30 17-
40o N Not visible Not visible Very low in the eastern sky during morning twilight at ~04:10 Low in the eastern sky during morning twilight at ~04:20 Low in the eastern sky during morning twilight at ~04:10 14-
Equator Not visible Not visible Not visible Very low in the eastern sky during morning twilight at ~05:10 Low in the eastern sky during morning twilight at ~05:00 19-
30o S Not visible Not visible Not visible Not visible Very low in the eastern sky during morning twilight at ~05:20 31-

C/2016 R2 (PANSTARRS): A far-northern evening comet visible in very large telescopes
This comet begins the month in Ursa Major at magnitude 12.0. Look for a 2.5' coma. It should fade slowly.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Low in the northern sky during evening twilight at ~23:00 Low in the northern sky during evening twilight at ~22:40 Low in the northern sky at ~22:40 Fairly high in the northern sky during evening twilight at ~21:00 Fairly high in the northern sky at ~21:10 1-
40o N Low in the northern sky during evening twilight at ~20:50 Low in the northern sky during evening twilight at ~20:40 Low in the northern sky during morning twilight at ~03:40 Low in the northern sky during evening twilight at ~20:00 Low in the northern sky during evening twilight at ~20:00 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/2015 O1 (PANSTARRS): An evening comet visible in very large telescopes
This comet begins the month in Ursa Major at magnitude 13.2. Look for a 1.5' coma. It should fade slowly.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N Low in the northern sky during evening twilight at ~22:50 Low in the northern sky during evening twilight at ~22:20 Low in the northern sky at ~22:40 Fairly high in the western sky during evening twilight at ~21:00 Low in the western sky during evening twilight at ~21:00 1-
40o N Fairly high in the western sky during evening twilight at ~21:00 Fairly high in the western sky during evening twilight at ~20:40 Fairly high in the western sky during evening twilight at ~20:20 Low in the western sky during evening twilight at ~20:00 Low in the western sky during evening twilight at ~20:00 1-
Equator Low in the western sky during evening twilight at ~19:20 Low in the western sky during evening twilight at ~19:10 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 1-26, 28-29
30o S Not visible Not visible Not visible Not visible Not visible 2-2

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 45" coma. It should remain constant.  FINDER CHART
Latitude Visibility August 4 Visibility August 11 Visibility August 18 Visibility August 25 Visibility September 1 Nights Visible
55o N High during evening twilight at ~23:00 High during evening twilight at ~22:40 Fairly high at ~22:40 High during evening twilight at ~21:00 Fairly high during evening twilight at ~21:10 1-
40o N High at ~21:10 High at ~21:00 Fairly high at ~23:20 High during evening twilight at ~20:10 High at ~20:10 1-
Equator High at ~19:50 High at ~19:30 High in moonlight at ~19:20 High in moonlight at ~19:20 High at ~19:20 1-
30o S Fairly high in the northern sky at ~19:50 Fairly high at ~19:10 Fairly high in moonlight at ~19:00 Fairly high during evening twilight at ~19:00 Fairly high at ~19:10 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

August 1st

August 15th

August 31st

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
C/2017 S3 (PANSTARRS) Auriga 7.2 5.5' 3.5 4.8' 8.6 2.9' 2018 July 24
C/2016 M1 (PANSTARRS) Circinus 8.7 4.8' 9.0 4.2' 9.3 3.7' 2018 July 30
21P/Giacobini-Zinner Cassiopeia 8.8 5.6' 7.9 6.8' 7.2 8.2' 2018 July 23
C/2017 T3 (ATLAS) Puppis 9.3 2.3' 9.9 2.2' 11.0 1.9' 2018 July 24
C/2018 N1 (NEOWISE) Scorpius 9.4 6.4' 11.1 3.0' 12.5 1.7' 2018 July 30
29P/Schwassmann-Wachmann Pisces 9.5 4.1' 9.4 4.2' 9.4 4.3' 2018 July 22
48P/Johnson Aquarius 9.7 6.3' 9.6 6.5' 9.6 6.5' 2018 July 22
66P/du Toit Cetus 10.2 4.0' 10.4 4.0' 10.8 3.9' 2018 July 22
37P/Forbes Pisces 10.6 5.2' 10.7 5.3' 10.9 5.2' 2018 July 22
C/2016 N6 (PANSTARRS) Cancer 11.9 2.6' 11.9 2.6' 11.9 2.7' 2018 July 9
C/2016 R2 (PANSTARRS) Ursa Major 12.0 2.6' 12.1 2.6' 12.2 2.6' 2018 July 15
364P/PANSTARRS Eridanus 12.5 48" 13.1 41" 14.0 32" 2018 July 24
C/2015 O1 (PANSTARRS) Ursa Major 13.2 1.3' 13.3 1.2' 13.4 1.2' 2018 July 14
38P/Stephan-Oterma Taurus 13.6 7" 12.7 7" 11.7 8" 2018 July 18
C/2017 M4 (ATLAS) Hercules 14.1 44" 14.1 43" 14.1 41" 2018 July 30

*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