Comet Chasing in September


Comet chasing is the visual observation of telescopic comets.

News


  • C/2017 O1 (ASASSN) is a new discovery on July 19 by the All-Sky Automated Survey for Supernovae (ASASSN) program. This program is designed to discover supernovae. This is its first comet discovery. It will reach perihelion in mid October, at which time the comet will pass within 0.7 AU of the earth. Maximum brightness may be around magnitude 7-8 at that time.

  • C/2015 V2 (Johnson) passed perihelion in mid June and is visible in small telescopes.. 

  • C/2015 ER61 (PANSTARRS) passed perihelion in early May and is on the way out, but remains bright enough to see in 6-inch (15 cm) telescopes. It had an outburst in early April, brightening by 1- 2 magnitudes. 

  • 29P/Schwassmann-Wachmann has been very active recently. On August 28 it had the second of two outbursts that occurred within a few days of one another. This second outburst was the brightest since 2010, brightening it up to 12th magnitude. On July 2 in had an outburst that for the first time was caught as the outburst occurred (see https://www.britastro.org/node/10684). 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. 

  • 240P/NEAT is in outburst, apparently brightening by 3 magnitudes. It may fade, so now is a good time to observe it.

  • C/2017 K2 (PANSTARRS) is a new discovery from the PANSTARRS survey. This comet was discovered at an unusually large distance, over 16 AU from the sun! It is currently magnitude 18.8, which is bright for that distance. It won't pass perihelion until October of 2023, apparently at distance of 1.7 AU from the sun. This might possibly be a Great Comet... or not. We will just have to wait (and wait, and wait, and wait) and see.  

  • C/2017 E4 (Lovejoy)  faded significantly on April 13, and appears to have disintegrated. There are no visual observations reported since it faded.  

  • 237P/LINEAR has not been observed visually since November when it was near perihelion. Afterward it was in conjunction with the Sun, but should have been picked up in morning twilight by the end of April. The last astrometry reported to the Minor Planet Center was in April. This comet was previously known as the asteroidal object 2002 LN13 but was recovered by WISE in 2010, appearing as a comet. It appears to have gone quiescent again, possibly as faint as 19th magnitude.  The next perihelion pass is in 2023. 

73P and fragment 73P-BT (lower right) on February 13. You can read an article about this image stack, and a movie made from the same set of images 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 September


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

C/2017 O1 (ASASSN): A morning comet visible in binoculars
This comet begins the month in Taurus at magnitude 9.0. Look for a 9.5' coma. It should brighten by about 1.0 magnitudes, moving into Perseus by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high at ~02:50 High during morning twilight at ~03:30 High in moonlight at ~03:20 High at ~03:30 High at ~03:30 1-
40o N High at ~03:50 High during morning twilight at ~04:10 High in moonlight at ~04:00 High at ~04:00 High at ~03:50 1-
Equator High at ~04:30 High in moonlight at ~04:40 High at ~03:30 High at ~04:00 High at ~03:50 1-
30o S High at ~04:40 High during morning twilight at ~04:50 Fairly high at ~04:00 Fairly high at ~04:00 Fairly high in the northern sky at ~03:40 1-

C/2015 ER61 (PANSTARRS): A morning comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Taurus, not far from the Pleiades, at magnitude 10.8. Look for a 3' coma. It should fade slowly.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N High at ~02:50 High during morning twilight at ~03:30 High in moonlight at ~03:20 High at ~03:20 High at ~03:10 1-
40o N High at ~03:50 High during morning twilight at ~04:10 High in moonlight at ~04:00 High at ~03:40 High at ~03:10 1-
Equator High at ~04:40 High in moonlight at ~04:40 High at ~03:30 High at ~03:40 High at ~03:10 1-
30o S Fairly high at ~04:40 Fairly high during morning twilight at ~04:50 Fairly high at ~04:00 Fairly high at ~03:40 Fairly high at ~03:10 1-

29P/Schwassmann-Wachmann: An evening comet visible in a 6-inch (15 cm) telescope
This comet begins the month in Aquarius, in outburst, at magnitude 12.1. It should fade, but further outbursts are likely. I will move into Capricornus by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Very low in the western sky at ~01:40 Low in the southern sky during evening twilight at ~20:10 Fairly high in the southern sky at ~21:20 Fairly high in the southern sky at ~21:00 Fairly high in the southern sky in moonlight at ~20:20 1-
40o N Low in the western sky at ~02:30 Fairly high at ~20:30 Fairly high at ~21:30 Fairly high at ~21:00 Fairly high in moonlight at ~20:00 1-
Equator Low in the western sky at ~03:30 High at ~20:50 High at ~21:30 High at ~21:00 High in moonlight at ~19:50 1-
30o S High in moonlight at ~22:10 High at ~21:10 High at ~21:30 High at ~21:10 High in moonlight at ~19:40 1-

C/2015 V2 (Johnson): A southern hemisphere evening comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Lupus at magnitude 10.6. Look for a 3.5' coma. It should fade by about 1.0 magnitudes, moving into Norma by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 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 during evening twilight at ~19:00 Fairly high in the southern sky at ~19:10 Fairly high in the southern sky at ~19:10 Fairly high in the southern sky in moonlight at ~19:00 Fairly high in the southern sky during evening twilight at ~18:50 1-
30o S High during evening twilight at ~19:00 High at ~19:20 High at ~19:20 High in moonlight at ~19:20 High during evening twilight at ~19:10 1-

C/2016 R2 (PANSTARRS): A morning comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in the middle of Orion, heading north toward the belt stars, at magnitude 13.5. Look for a 1.5' coma. It should brighten by about 0.6 magnitudes by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Low in the eastern sky during morning twilight at ~03:10 Fairly high in the southern sky during morning twilight at ~03:40 Fairly high in the southern sky during morning twilight at ~03:30 Fairly high in the southern sky at ~03:40 Fairly high at ~03:50 1-
40o N Fairly high at ~03:50 Fairly high during morning twilight at ~04:20 High in moonlight at ~04:10 High at ~04:10 High at ~04:20 1-
Equator High at ~04:40 High during morning twilight at ~04:50 High in moonlight at ~04:40 High at ~04:30 High at ~04:30 1-
30o S High at ~04:50 High during morning twilight at ~04:50 High at ~04:10 High at ~04:20 High at ~04:10 1-

71P/Clark: An evening comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Corona Australis at magnitude 13.0. Look for a 55" coma. It should fade by about 1.0 magnitudes, moving into Sagittarius by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Low in the southern sky during evening twilight at ~19:40 Low in the southern sky during evening twilight at ~19:50 Low in the southern sky during evening twilight at ~19:40 Low in the southern sky during evening twilight at ~19:20 Low in the southern sky during evening twilight at ~19:00 1-
Equator High in moonlight at ~19:10 High at ~19:20 High at ~19:20 High in moonlight at ~19:10 High during evening twilight at ~19:00 1-
30o S High in moonlight at ~19:10 High at ~19:20 High at ~19:30 High in moonlight at ~19:30 High during evening twilight at ~19:20 1-

C/2015 O1 (PANSTARRS): An evening comet visible in a 16-inch (41 cm) telescope
This comet begins the month in Hercules at magnitude 14.1. Look for a 25" coma. It should remain constant.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N High during evening twilight at ~20:40 High during evening twilight at ~20:10 Fairly high during evening twilight at ~20:20 Fairly high during evening twilight at ~20:00 Fairly high during evening twilight at ~19:20 1-
40o N High during evening twilight at ~19:50 High at ~19:50 High at ~19:40 High at ~19:30 High during evening twilight at ~19:00 1-
Equator High during evening twilight at ~19:10 High at ~19:10 High at ~19:10 Fairly high in moonlight at ~19:00 Fairly high during evening twilight at ~18:50 1-
30o S Fairly high during evening twilight at ~18:50 Fairly high in the northern sky at ~19:10 Fairly high in the northern sky during evening twilight at ~19:10 Fairly high in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~19:00 1-

213P/Van Ness: An evening comet visible in an 18-inch (46 cm) telescope
This comet begins the month in Sagittarius at magnitude 13.7. Look for a 45" coma. It should fade slowly. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Low in the southern sky during evening twilight at ~20:30 Low in the southern sky during evening twilight at ~20:10 Low in the southern sky during evening twilight at ~20:10 Low in the southern sky during evening twilight at ~19:50 Low in the southern sky during evening twilight at ~19:20 1-
40o N Fairly high in the southern sky during evening twilight at ~20:00 Fairly high in the southern sky at ~20:00 Fairly high in the southern sky at ~19:50 Fairly high in the southern sky at ~20:00 Fairly high in the southern sky during evening twilight at ~19:00 1-
Equator High in moonlight at ~19:50 High at ~19:50 High at ~19:30 High in moonlight at ~19:20 High during evening twilight at ~19:00 1-
30o S High in moonlight at ~20:00 High at ~19:50 High at ~19:30 High in moonlight at ~19:30 High during evening twilight at ~19:20 1-

217P/LINEAR: A morning comet visible in very large telescopes
This comet begins the month in Orion at magnitude 12.9. Look for a 2' coma. It should fade by about 0.5 magnitudes, moving into Canis Minor by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high in the eastern sky during morning twilight at ~03:00 Fairly high in the eastern sky during morning twilight at ~03:40 Fairly high in the eastern sky during morning twilight at ~03:30 Fairly high during morning twilight at ~03:50 Fairly high at ~04:00 1-
40o N Fairly high at ~03:50 Fairly high during morning twilight at ~04:20 Fairly high in moonlight at ~04:10 High at ~04:20 High at ~04:20 1-
Equator High at ~04:40 High during morning twilight at ~04:50 High in moonlight at ~04:40 High at ~04:40 High at ~04:30 1-
30o S Fairly high at ~04:50 Fairly high during morning twilight at ~05:00 Fairly high at ~04:30 Fairly high at ~04:30 Fairly high at ~04:20 1-

96P/Machholz: A southern hemisphere evening comet visible in very large telescopes
This comet begins the month in Circinus at magnitude 15.0. Look for a 6.5' coma. It should brighten rapidly, moving into Centaurus by month's end. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 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 ~19:00 Low in the southern sky during evening twilight at ~19:00 Very low in the southern sky during evening twilight at ~19:00 Very low in the southern sky during evening twilight at ~18:50 Not visible 1-28
30o S High during evening twilight at ~19:00 Fairly high at ~19:10 Fairly high at ~19:10 Fairly high in the southern sky in moonlight at ~19:20 Fairly high in the southern sky during evening twilight at ~19:10 1-

62P/Tsuchinshan: A morning comet visible in very large telescopes
This comet begins the month in Gemini at magnitude 14.6. Look for a 4' coma. It should brighten by about 1.3 magnitudes, moving into Cancer by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Fairly high in the eastern sky during morning twilight at ~03:00 Fairly high during morning twilight at ~03:40 Fairly high in the eastern sky during morning twilight at ~03:30 Fairly high at ~03:40 Fairly high at ~04:00 1-
40o N Fairly high at ~03:50 Fairly high during morning twilight at ~04:20 Fairly high in moonlight at ~04:10 High at ~04:20 High at ~04:20 1-
Equator Fairly high at ~04:50 High during morning twilight at ~04:50 Fairly high in moonlight at ~04:40 Fairly high at ~04:40 Fairly high at ~04:40 1-
30o S Fairly high in the eastern sky during morning twilight at ~04:50 Fairly high in the eastern sky during morning twilight at ~05:00 Fairly high in the eastern sky during morning twilight at ~04:40 Fairly high in the eastern sky during morning twilight at ~04:30 Fairly high in the eastern sky during morning twilight at ~04:20 1-

240P/NEAT: An evening comet visible in very large telescopes
This comet begins the month in Sculptor at magnitude 14.0. Look for a 50" coma. It should brighten slowly. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Low in the southern sky at ~02:30 Low in the southern sky in moonlight at ~01:20 Low in the southern sky at ~00:50 Low in the southern sky at ~00:10 Low in the southern sky at ~01:10 1-
Equator High at ~03:30 Low in the eastern sky at ~20:50 High at ~00:50 High at ~00:10 Fairly high at ~02:10 1-
30o S High at ~04:10 Fairly high at ~21:10 High at ~00:50 High at ~00:10 High at ~02:50 1-

C/2015 VL62 (Lemmon-Yeung-PANSTARRS): An evening comet visible in very large telescopes
This comet begins the month in Aquarius at magnitude 13.6. Look for a 60" coma. It should fade by about 0.5 magnitudes, moving into Aquila by month's end.  FINDER CHART
Latitude Visibility September 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Low in the western sky at ~01:40 Fairly high during evening twilight at ~20:10 Fairly high in the southern sky at ~20:40 Fairly high in the southern sky at ~20:10 Fairly high in the southern sky during evening twilight at ~19:20 1-
40o N Low in the western sky at ~02:30 High at ~20:30 High at ~20:20 High at ~20:00 Fairly high during evening twilight at ~19:10 1-
Equator High in moonlight at ~21:50 High at ~20:50 High at ~20:20 High at ~20:40 High during evening twilight at ~19:00 1-
30o S High in moonlight at ~21:50 High at ~21:10 High at ~20:20 High in moonlight at ~19:40 High during evening twilight at ~19:20 1-

P/1906 UA (Scheila): An evening comet visible in very large telescopes
This comet begins the month in Scorpius at magnitude 13.8. 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 2 Visibility September 9 Visibility September 16 Visibility September 23 Visibility September 30 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible  
40o N Low in the southern sky during evening twilight at ~19:40 Low in the southern sky during evening twilight at ~19:40 Low in the southern sky during evening twilight at ~19:30 Low in the southern sky during evening twilight at ~19:20 Low in the southern sky during evening twilight at ~18:50 1-
Equator High during evening twilight at ~19:10 High at ~19:10 High at ~19:10 High in moonlight at ~19:10 High during evening twilight at ~18:50 1-
30o S High during evening twilight at ~19:00 High at ~19:20 High at ~19:20 High in moonlight at ~19:20 High during evening twilight 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

September 1st

September 15th

September 30th

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
C/2017 O1 (ASASSN) Taurus 9.0 7.1' 8.5 8.3' 8.0 9.6' 2017 September 1
C/2015 V2 (Johnson) Lupus 10.7 3.9' 11.1 3.5' 11.6 3.1' 2017 August 23
C/2015 ER61 (PANSTARRS) Taurus 10.8 3.0' 11.0 3.0' 11.1 3.0' 2017 September 1
29P/Schwassmann-Wachmann Aquarius 12.1 57" 12.1 56" 12.2 54" 2017 September 2
217P/LINEAR Orion 12.9 2.0' 13.1 2.0' 13.4 2.0' 2017 September 2
71P/Clark Corona Australis 13.0 56" 13.5 50" 14.0 43" 2017 August 23
C/2016 R2 (PANSTARRS) Orion 13.5 1.1' 13.3 1.2' 12.9 1.3' 2017 August 13
C/2015 VL62 (Lemmon-Yeung-PANSTARRS) Aquarius 13.6 1.0' 13.8 56" 14.2 48" 2017 August 30
213P/Van Ness Sagittarius 13.7 45" 13.9 41" 14.1 37" 2017 August 14
P/1906 UA (Scheila) Scorpius 13.8 0" 13.9 0" 14.1 0" 2017 August 1
240P/NEAT Sculptor 14.0 50" 13.8 52" 13.7 52" 2017 September 2
C/2015 O1 (PANSTARRS) Hercules 14.2 24" 14.2 24" 14.2 23" 2017 August 14
C/2016 M1 (PANSTARRS) Hercules 14.6 24" 14.5 24" 14.4 24" 2017 August 22
65P/Gunn Scorpius 14.6 46" 14.7 43" 14.9 41" 2017 July 1
C/2016 N4 (MASTER) Cepheus 14.7 6" 14.7 6" 14.7 6" 2017 August 21
C/2016 N6 (PANSTARRS) Bootes 14.9 24" 14.8 24" 14.6 25" 2017 August 18
96P/Machholz Circinus 16.0 32" 15.0 33" 13.3 34" 2017 August 6

*In solar conjunction and generally not visible

For the latest news and comet observations see the ICQ/CBAT/MPC: Recent Comet Magnitude Estimates page.  The Astronomical Headlines page of the IAU is also a good source of information, particularly for recent discoveries.

For general information about 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