Comet Chasing in July


Comet chasing is the visual observation of telescopic comets.

News


July offers two binocular comets and a total of five comets visible in small telescopes.
  • C/2020 F3 (NEOWISE) will reach perihelion in early July. In late July this comet will pass within 0.7 AU of the earth. It is currently predicted to reach maximum brightness of magnitude 4 in early July.

  • A/2019 U6 (Lemmon). This asteroid was observed to have a cometary coma in early February, apparently noted by A. Novichonok. It passed perihelion on June 18. 

  • C/2017 T2 (PANSTARRS) passed perihelion in early May. 

  • 88P/Howell will reach perihelion in late September. It is predicted to reach maximum brightness of magnitude 9.5 in mid September

  • C/2020 F8 (SWAN) was discovered on SWAN images on April 9. It passed perihelion on May 26 and  in late May it passed within 0.8 AU of the earth. It is currently a naked-eye object..

  • C/2019 Y4 (ATLAS). This comet had the potential to become a bright naked-eye object near perihelion in late May, but on April 8 it was observed in images to have fragmented. The smaller fragments have separated and begun to fade. The visible coma has faded signifficantly. The remnants likely reached maximum brightness in late May.  

  • 2P/Encke will passed perihelion on June 25. In late July this comet will pass within 0.6 AU of the earth. It is predicted to reach maximum brightness of magnitude ~5 in late July. 

  • 58P/Jackson-Neujmion passed periehlion in late May. 

  • C/2019 Y1 (ATLAS) passed perihelion in March.

  • 210P/Christensen passed perihelion in early April.

  • 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...

  • 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. 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.

C/2019 Y4 (ATLAS) broke up in early April, as seen in these HST images, but the brightest component remains observable

Comet Visibility in the Eyepiece

This page uses code developed for SkyTools 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 July


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

C/2020 F3 (NEOWISE): An evening comet visible in binoculars
This comet begins the month in Taurus at magnitude 5.4. Look for a 10.5' coma. It should fade rapidly, moving into Coma Berenices by month's end.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 1 Nights Visible
55o N Not visible Very low in the northern sky during morning twilight at ~00:40 Low in the northern sky during evening twilight at ~23:50 Low in the northern sky during evening twilight at ~23:20 Fairly high in the western sky during evening twilight at ~22:00 2-
40o N Very low in the eastern sky during morning twilight at ~03:40 Very low in the northern sky during morning twilight at ~03:20 Low in the northern sky during evening twilight at ~21:10 Fairly high in the western sky during evening twilight at ~21:10 Fairly high during evening twilight at ~20:40 1-
Equator Not visible Not visible Not visible Low in the western sky during evening twilight at ~19:20 Fairly high during evening twilight at ~19:10 1-7, 18-
30o S Not visible Not visible Not visible Very low in the northern sky during evening twilight at ~18:30 Fairly high in the northern sky during evening twilight at ~18:30 24-

C/2019 U6 (Lemmon): An evening comet visible in binoculars
This comet begins the month in Sextans at magnitude 7.1. Look for a 8.5' coma. It should fade rapidly, moving into Coma Berenices by month's end.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 1 Nights Visible
55o N Not visible Not visible Low in the western sky during evening twilight at ~22:30 Low in the western sky during evening twilight at ~22:40 Fairly high in the western sky during evening twilight at ~22:00 6-
40o N Low in the western sky during evening twilight at ~20:50 Low in the western sky during evening twilight at ~21:10 Fairly high in the western sky during evening twilight at ~21:10 Fairly high in the western sky during evening twilight at ~21:00 Fairly high during evening twilight at ~20:40 1-
Equator High during evening twilight at ~19:10 High at ~19:30 High at ~19:30 High in moonlight at ~19:20 High during evening twilight at ~19:10 1-
30o S High during evening twilight at ~18:30 Fairly high at ~18:50 Fairly high at ~18:50 Fairly high during evening twilight at ~18:50 Fairly high during evening twilight at ~18:40 1-

2P/Encke: An evening comet visible in small telescopes
This comet begins the month in Cancer at magnitude 5.0. Look for a 8' coma. It should fade rapidly, moving into Corvus by month's end. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 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 1-7
Equator Very low in the western sky during evening twilight at ~19:00 Low in the western sky during evening twilight at ~19:10 Low in the western sky during evening twilight at ~19:20 Fairly high in the western sky during evening twilight at ~19:20 Fairly high during evening twilight at ~19:10 1-
30o S Low in the western sky during evening twilight at ~18:10 Low in the western sky during evening twilight at ~18:40 Fairly high in the western sky during evening twilight at ~18:40 Fairly high during evening twilight at ~18:40 High during evening twilight at ~18:40 1-

C/2017 T2 (PANSTARRS): An evening comet visible in small telescopes
This comet begins the month in Canes Venatici at magnitude 9.7. Look for a 3' coma. It should fade by about 0.9 magnitudes, moving into Coma Berenices by month's end.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 1 Nights Visible
55o N Fairly high during evening twilight at ~23:30 Fairly high in the western sky during evening twilight at ~23:30 Fairly high in the western sky during evening twilight at ~23:30 Low in the western sky during evening twilight at ~23:10 Fairly high in the western sky during evening twilight at ~22:00 1-
40o N High during evening twilight at ~21:10 High at ~21:30 Fairly high during evening twilight at ~21:20 Fairly high during evening twilight at ~21:10 Fairly high during evening twilight at ~20:40 1-
Equator High during evening twilight at ~19:20 High at ~19:30 High at ~19:30 High in moonlight at ~19:20 High during evening twilight at ~19:10 1-
30o S Fairly high in the northern sky during evening twilight at ~18:30 Fairly high in the northern sky at ~18:50 Fairly high in the northern sky at ~18:50 Fairly high during evening twilight at ~18:50 Fairly high during evening twilight at ~18:40 1-

88P/Howell: An evening comet visible in small telescopes
This comet begins the month in Virgo at magnitude 10.5. Look for a 3.5' coma. It should brighten by about 0.5 magnitudes by month's end. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 1 Nights Visible
55o N Not visible Not visible Not visible Not visible Not visible 1-28, 30-30
40o N Fairly high in the western sky during evening twilight at ~21:00 Fairly high in the western sky during evening twilight at ~21:20 Fairly high in the western sky during evening twilight at ~21:10 Low in the western sky during evening twilight at ~20:50 Low in the western sky during evening twilight at ~20:30 1-
Equator High during evening twilight at ~19:20 High at ~19:30 High at ~19:30 High in moonlight at ~19:20 High during evening twilight at ~19:10 1-
30o S High in moonlight at ~18:50 High at ~18:50 High at ~18:50 High in moonlight at ~18:50 High during evening twilight at ~18:40 1-

58P/Jackson-Neujmin: A morning comet visible in an 8-inch (20 cm) telescope
This comet begins the month in Taurus at magnitude 11.0. Look for a 2.5' coma. It should fade by about 0.6 magnitudes, moving into Orion by month's end.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 1 Nights Visible
55o N Not visible Not visible Not visible Very low in the eastern sky during morning twilight at ~02:10 Very low in the eastern sky during morning twilight at ~02:10 12-
40o N Low in the eastern sky during morning twilight at ~03:20 Low in the eastern sky during morning twilight at ~03:20 Low in the eastern sky during morning twilight at ~03:10 Low in the eastern sky during morning twilight at ~03:20 Low in the eastern sky during morning twilight at ~03:20 1-
Equator Fairly high during morning twilight at ~05:00 Fairly high during morning twilight at ~05:00 Fairly high in the eastern sky at ~04:50 Fairly high at ~04:50 Fairly high during morning twilight at ~04:50 1-
30o S Fairly high in the eastern sky during morning twilight at ~05:50 Fairly high in the eastern sky during morning twilight at ~05:40 Fairly high in the eastern sky at ~05:30 Fairly high in the eastern sky at ~05:20 Fairly high during morning twilight at ~05:40 1-

C/2018 A6 (Gibbs): A morning comet visible in a 10-inch (25 cm) telescope
This comet begins the month in Sculptor at magnitude 13.5. Look for a 15" coma. It should remain constant. The best visibility is early in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 1 Nights Visible
55o N Not visible Not visible Not visible Not visible Very low in the southern sky during morning twilight at ~02:20 30-
40o N Low in the southern sky during morning twilight at ~03:20 Low in the southern sky during morning twilight at ~03:10 Low in the southern sky during morning twilight at ~03:00 Low in the southern sky during morning twilight at ~03:00 Low in the southern sky during morning twilight at ~03:20 1-
Equator High in moonlight at ~04:30 High in moonlight at ~04:40 High at ~04:10 High at ~03:30 High during morning twilight at ~04:50 1-
30o S High in moonlight at ~04:40 High in moonlight at ~04:50 High at ~04:10 High at ~03:30 High during morning twilight at ~05:50 1-

C/2019 Y1 (ATLAS): An evening comet visible in a 12.5-inch (32 cm) telescope
This comet begins the month in Coma Berenices at magnitude 12.1. Look for a 1.5' coma. It should fade by about 1.5 magnitudes, moving into Virgo by month's end.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 1 Nights Visible
55o N Low in the western sky during evening twilight at ~23:00 Low in the western sky during evening twilight at ~23:10 Low in the western sky during evening twilight at ~22:40 Very low in the western sky during evening twilight at ~22:10 Not visible 1-
40o N Fairly high during evening twilight at ~21:00 Fairly high in the western sky during evening twilight at ~21:20 Fairly high in the western sky during evening twilight at ~21:10 Fairly high in the western sky during evening twilight at ~21:00 Fairly high in the western sky during evening twilight at ~20:30 1-
Equator High during evening twilight at ~19:20 High at ~19:30 High at ~19:30 High during evening twilight at ~19:20 High during evening twilight at ~19:10 1-
30o S Fairly high during evening twilight at ~18:30 Fairly high at ~18:50 Fairly high at ~18:50 Fairly high during evening twilight at ~18:40 Fairly high during evening twilight at ~18:40 1-

C/2018 F4 (PANSTARRS): A morning comet visible in an 18-inch (46 cm) telescope
This comet begins the month in Fornax at magnitude 14.0. Look for a 45" coma. It should remain constant. The best visibility is late in the month as seen from the southern hemisphere.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 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 Very low in the southern sky during morning twilight at ~03:50 30-
Equator Fairly high during morning twilight at ~05:00 Fairly high during morning twilight at ~05:00 Fairly high at ~04:50 High at ~04:50 High during morning twilight at ~04:50 1-
30o S High during morning twilight at ~05:40 High during morning twilight at ~05:30 High at ~05:20 High at ~05:20 High during morning twilight at ~05:30 1-

246P/NEAT: An evening comet visible in an 18-inch (46 cm) telescope
This comet begins the month in Virgo at magnitude 14.1. Look for a 45" coma. It should fade slowly.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 1 Nights Visible
55o N Low in the western sky during evening twilight at ~22:50 Low in the western sky during evening twilight at ~22:50 Low in the western sky during evening twilight at ~22:30 Very low in the western sky during evening twilight at ~22:10 Low in the western sky during evening twilight at ~21:40 1-
40o N Fairly high during evening twilight at ~21:00 Fairly high in the western sky during evening twilight at ~21:20 Fairly high in the western sky during evening twilight at ~21:10 Fairly high in the western sky during evening twilight at ~21:00 Fairly high in the western sky during evening twilight at ~20:30 1-
Equator High during evening twilight at ~19:20 High at ~19:30 High at ~19:30 High during evening twilight at ~19:20 High during evening twilight at ~19:10 1-
30o S High in moonlight at ~18:40 High at ~18:50 High at ~18:50 High during evening twilight at ~18:40 High during evening twilight at ~18:40 1-

C/2019 N1 (ATLAS): An evening comet visible in very large telescopes
This comet begins the month in Ursa Major at magnitude 13.2. Look for a 2.5' coma. It should brighten slowly, moving into Canes Venatici by month's end.  FINDER CHART
Latitude Visibility July 4 Visibility July 11 Visibility July 18 Visibility July 25 Visibility August 1 Nights Visible
55o N Fairly high during evening twilight at ~23:40 Fairly high during evening twilight at ~23:30 Fairly high in the northern sky during evening twilight at ~23:50 Fairly high in the western sky during evening twilight at ~23:30 Fairly high in the western sky during evening twilight at ~22:10 1-
40o N High during evening twilight at ~21:10 Fairly high at ~21:30 Fairly high at ~21:20 Fairly high during evening twilight at ~21:10 Fairly high during evening twilight at ~20:40 1-
Equator Fairly high in the northern sky during evening twilight at ~19:10 Fairly high in the northern sky at ~19:30 Fairly high in the northern sky at ~19:20 Fairly high in the northern sky during evening twilight at ~19:20 Fairly high in the northern sky during evening twilight at ~19:10 1-
30o S Not visible Very low in the northern sky during evening twilight at ~18:30 Very low in the northern sky during evening twilight at ~18:30 Very low in the northern sky during evening twilight at ~18:30 Very low in the northern sky during evening twilight at ~18:20 6-

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

July 1st

July 15th

July 31st

Observations as of (UT)
Mag Diam Mag Diam Mag Diam
C/2020 F3 (NEOWISE) Taurus 5.4 5.9' 5.7 9.3' 7.7 9.5' 2020 June 21
C/2019 U6 (Lemmon) Sextans 7.1 8.5' 7.7 7.7' 8.8 6.3' 2020 June 30
2P/Encke Cancer 7.4 36" 9.8 50" 12.0 1.0' 2020 June 30
C/2017 T2 (PANSTARRS) Canes Venatici 9.7 3.1' 10.1 2.9' 10.6 2.6' 2020 June 30
88P/Howell Virgo 10.5 3.9' 10.3 3.8' 10.0 3.7' 2020 June 21
58P/Jackson-Neujmin Taurus 11.0 2.6' 11.3 2.6' 11.6 2.6' 2020 June 22
C/2019 Y1 (ATLAS) Coma Berenices 12.1 1.8' 12.8 1.5' 13.5 1.3' 2020 June 21
C/2020 F8 (SWAN) Auriga 13.3 2.5' 14.5 2.2' 15.6 2.1' 2020 June 2
C/2019 Y4 (ATLAS) Orion 13.4 4.6' 15.0 4.0' 16.2 3.5' 2020 May 22
C/2018 N2 (ASASSN) Cepheus 13.7 3.4' 13.8 3.4' 14.0 3.4' 2020 June 24
29P/Schwassmann-Wachmann Aries 13.8 1.6' 13.7 1.6' 13.6 1.7' 2020 May 26
C/2018 F4 (PANSTARRS) Fornax 14.0 44" 14.0 45" 14.0 46" 2020 April 24
246P/NEAT Virgo 14.1 48" 14.1 46" 14.2 43" 2020 June 21
C/2019 N1 (ATLAS) Ursa Major 14.8 51" 14.6 51" 14.3 51" 2020 June 24
C/2017 K2 (PANSTARRS) Draco 15.4 48" 15.3 49" 15.2 49" 2020 June 24
C/2020 F5 (MASTER) Apus 15.4 20" 15.4 20" 15.3 20" 2020 June 6
210P/Christensen Leo 15.9 57" 16.7 49" 17.5 43" 2020 June 24
*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

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