Comet Chasing in October


Comet chasing is the visual observation of telescopic comets.

News


This month brings the slimmest pickings for telescopic comets in recent memory.
  • 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/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 W2 (Africano) will reach perihelion in early September. In late September this comet will pass within 0.5 AU of the earth, when it is predicted to reach maximum brightness of magnitude 8.8.

  • 260P/McNaught will reach perihelion in early September. In early October this comet will pass within 0.6 AU of the earth. It is predicted to reach maximum brightness of magnitude ~10.5 in late September

  • C/2018 N2 (ASASSN) will reach perihelion in mid November. It is predicted to reach maximum brightness of magnitude 11.5 in late October.

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

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

  • C/2018 R3 (Lemmon) passed perihelion in early June. 

  • 168P/Hergenrother passed perihelion in early August but has not been recovered. In July it was fainter than 19th magnitude.

  • C/2019 A9 (PANSTARRS) passed perihelion in late July.

  • C/2018 Y1 (Iwamoto) is past perihelion, which occurred in early February.

  • C/2017 B3 (LINEAR) is past perihelion, which occurred in early February.

  • 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. 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 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.

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 October


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

C/2017 T2 (PANSTARRS): A morning comet visible in binoculars
This comet begins the month in Taurus at magnitude 7.0. Look for a 14.5' coma. It should brighten by about 1.0 magnitudes, moving into Auriga by month's end.  FINDER CHART
Latitude Visibility September 28 Visibility October 5 Visibility October 12 Visibility October 19 Visibility October 26 Nights Visible
55o N High at ~03:40 High at ~03:50 High in moonlight at ~03:10 Low in the eastern sky at ~20:10 High at ~03:20 1-
40o N High at ~04:10 High at ~04:10 High in moonlight at ~03:10 Low in the eastern sky at ~21:10 High at ~03:20 1-
Equator High at ~04:30 High at ~04:20 High in moonlight at ~03:30 Low in the eastern sky at ~22:40 High at ~03:20 1-
30o S Fairly high at ~04:10 Fairly high at ~04:00 Fairly high in the northern sky in moonlight at ~03:50 Fairly high in the northern sky in moonlight at ~03:50 Fairly high in the northern sky at ~03:20 1-

C/2018 W2 (Africano): An evening comet visible in binoculars
This comet begins the month in Pisces at magnitude 8.7. Look for a 7' coma. It should fade rapidly, moving into Grus by month's end.  FINDER CHART
Latitude Visibility September 28 Visibility October 5 Visibility October 12 Visibility October 19 Visibility October 26 Nights Visible
55o N High at ~23:10 Fairly high in the southern sky at ~22:00 Low in the southern sky in moonlight at ~21:00 Not visible Not visible 1-22
40o N High at ~23:10 Fairly high at ~22:40 Fairly high in the southern sky in moonlight at ~21:00 Low in the southern sky at ~20:10 Low in the southern sky at ~19:30 1-
Equator High at ~23:20 High at ~00:10 High in moonlight at ~21:00 High at ~20:10 High at ~19:30 1-
30o S High at ~23:20 High at ~01:10 High in moonlight at ~21:00 High at ~20:10 High at ~20:00 1-

C/2018 N2 (ASASSN): An evening comet visible in small telescopes
This comet begins the month in Triangulum at magnitude 11.0. Look for a 2' coma. It should remain constant, moving into Andromeda by month's end.  FINDER CHART
Latitude Visibility September 28 Visibility October 5 Visibility October 12 Visibility October 19 Visibility October 26 Nights Visible
55o N High at ~01:30 High at ~00:50 High in moonlight at ~00:00 High at ~20:10 High at ~22:40 1-
40o N High at ~01:30 High at ~00:50 High in moonlight at ~00:00 High at ~21:10 High at ~22:40 1-
Equator High at ~01:30 High at ~00:50 High in moonlight at ~00:00 High at ~22:40 High at ~22:40 1-
30o S Fairly high in the northern sky at ~01:30 Fairly high in the northern sky at ~01:10 Fairly high in the northern sky in moonlight at ~00:00 Fairly high in the northern sky at ~23:20 Fairly high in the northern sky at ~22:40 1-

260P/McNaught: A morning comet visible in small telescopes
This comet begins the month in Perseus at magnitude 11.2. Look for a 2' coma. It should fade slowly.  FINDER CHART
Latitude Visibility September 28 Visibility October 5 Visibility October 12 Visibility October 19 Visibility October 26 Nights Visible
55o N High at ~02:20 High at ~02:00 High in moonlight at ~01:10 High at ~20:10 High at ~00:20 1-
40o N High at ~02:20 High at ~01:50 High in moonlight at ~01:20 High at ~21:10 High at ~00:20 1-
Equator High at ~02:20 High at ~02:00 High in moonlight at ~01:20 Fairly high at ~22:40 High at ~00:20 1-
30o S Fairly high in the northern sky at ~02:20 Low in the northern sky at ~01:50 Low in the northern sky in moonlight at ~01:30 Low in the northern sky at ~23:40 Low in the northern sky at ~00:20 1-

C/2018 Y1 (Iwamoto): A morning comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Perseus at magnitude 12.6. Look for a 1' coma. It should fade slowly, moving into Andromeda by month's end.  FINDER CHART
Latitude Visibility September 28 Visibility October 5 Visibility October 12 Visibility October 19 Visibility October 26 Nights Visible
55o N High at ~02:50 High at ~02:10 High in moonlight at ~01:10 High at ~20:10 High at ~23:50 1-
40o N High at ~03:00 High at ~02:10 High in moonlight at ~01:10 High at ~21:10 High at ~23:50 1-
Equator High at ~03:00 High at ~02:10 High in moonlight at ~01:20 High at ~22:40 High at ~23:50 1-
30o S Low in the northern sky at ~03:00 Low in the northern sky at ~02:10 Low in the northern sky in moonlight at ~01:20 Low in the northern sky at ~23:40 Low in the northern sky at ~23:50 1-

C/2019 A9 (PANSTARRS): A southern hemisphere morning comet visible in an 18-inch (46 cm) telescope
This comet begins the month in Centaurus at magnitude 13.0. Look for a 60" coma. It should fade by about 1.0 magnitudes, 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 28 Visibility October 5 Visibility October 12 Visibility October 19 Visibility October 26 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 Fairly high in the southern sky during morning twilight at ~04:20 Low in the southern sky during morning twilight at ~04:10 Low in the southern sky during morning twilight at ~04:20 Low in the southern sky during evening twilight at ~19:30 Low in the southern sky during evening twilight at ~19:40 1-

C/2018 R3 (Lemmon): A morning comet visible in very large telescopes
This comet begins the month in Sextans at magnitude ~12. Look for a ~4' coma. It should fade by about 0.6 magnitudes, moving into Crater by month's end.  FINDER CHART
Latitude Visibility September 28 Visibility October 5 Visibility October 12 Visibility October 19 Visibility October 26 Nights Visible
55o N Very low in the eastern sky during morning twilight at ~04:30 Very low in the eastern sky during morning twilight at ~04:40 Low in the eastern sky during morning twilight at ~05:00 Low in the eastern sky during morning twilight at ~05:00 Low in the eastern sky during morning twilight at ~05:00 1-
40o N Very low in the eastern sky during morning twilight at ~04:40 Low in the eastern sky during morning twilight at ~04:40 Low in the eastern sky during morning twilight at ~05:00 Low in the eastern sky during morning twilight at ~05:00 Low in the eastern sky during morning twilight at ~04:50 1-
Equator Very low in the eastern sky during morning twilight at ~04:50 Low in the eastern sky during morning twilight at ~04:40 Fairly high 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 ~04:30 1-
30o S Very low in the eastern sky during morning twilight at ~04:40 Very low in the eastern sky during morning twilight at ~04:20 Low in the eastern sky during morning twilight at ~04:30 Low in the eastern sky during morning twilight at ~04:10 Low in the eastern sky during morning twilight at ~03:50 1-

29P/Schwassmann-Wachmann: An evening comet visible in very large telescopes
This comet begins the month in Pisces at magnitude 13.5. Look for a 3.5' coma. It should remain constant.  FINDER CHART
Latitude Visibility September 28 Visibility October 5 Visibility October 12 Visibility October 19 Visibility October 26 Nights Visible
55o N High at ~00:20 High at ~23:50 High in moonlight at ~23:00 Fairly high at ~20:10 High at ~22:10 1-
40o N High at ~00:20 High at ~23:50 High in moonlight at ~23:00 High at ~21:10 High at ~22:10 1-
Equator High at ~00:20 High at ~00:10 High in moonlight at ~23:10 High at ~22:40 High at ~22:10 1-
30o S High at ~00:20 High at ~01:10 High in moonlight at ~23:10 High at ~22:40 High at ~22:10 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

October 1st

October 15th

October 31st

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
C/2018 W2 (Africano) Pisces 8.9 8.5' 9.9 5.7' 11.2 3.6' 2019 October 1
C/2017 T2 (PANSTARRS) Taurus 9.4 6.1' 9.0 6.9' 8.4 8.1' 2019 September 29
C/2018 N2 (ASASSN) Triangulum 10.8 3.1' 10.7 3.2' 10.7 3.1' 2019 September 29
260P/McNaught Perseus 11.2 2.0' 11.3 2.0' 11.6 1.9' 2019 September 29
C/2018 R3 (Lemmon) Sextans ~12 ~4' ~12 ~4' ~12.5 ~4' 2019 July 6
C/2019 A9 (PANSTARRS) Centaurus 13.0 59" 13.4 55" 13.9 49" 2019 August 29
68P/Klemola Serpens Cauda 13.3 1.3' 13.4 1.2' 13.5 1.2' 2019 October 1
C/2018 A6 (Gibbs) Chamaeleon 14.1 44" 14.2 43" 14.3 42" 2019 October 1
C/2017 B3 (LINEAR) Grus 14.5 58" 14.7 55" 14.8 52" 2019 October 1
C/2016 M1 (PANSTARRS) Canis Major 14.6 3.0' 14.7 3.0' 14.8 3.0' 2019 August 24
29P/Schwassmann-Wachmann Pisces 14.8 49" 14.8 49" 14.8 48" 2019 October 1
78P/Gehrels Cancer 15.0 50" 15.1 52" 15.2 55" 2019 September 6
C/2018 Y1 (Iwamoto) Perseus 15.4 12" 15.5 12" 15.8 12" 2019 September 24
101P/Chernykh Aquarius 15.6 19" 15.5 18" 15.5 18" 2019 September 8
261P/Larson Taurus 15.8 20" 15.7 21" 15.8 22" 2019 September 6
2I/Borisov (C/2019 Q4) Leo 16.7 50" 16.1 55" 15.6 1.0' 2019 September 25
*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