Comet Chasing in October
Comet chasing is the visual observation of telescopic comets. Jump to: Observing synopses Summary data Buy me a Coffee
We have a comet visible to the naked-eye, and another visible in binoculars this month! See the Observing Synopses for which comets are visible from your latitude, the best dates and the time of night.
3I/ATLAS is a new interstellar comet discovery. It is currently magnitude 12.7 at a distance of 2.5 AU. It will pass closest to the sun on October 29 at a distance of 1.4 AU. Best viewing will likely be with large telescopes in November from both hemispheres. We'll have more observing information as it brightens.
C/2025 A6 (Lemmon) - is an intriguing comet that brightened quickly in late August and has now become a naked eye object.
C/2025 R2 (SWAN) was identified by Vladimir Bezugly in SWAN images around 2025-09-11 (visible in SWAN since at least Sep 4, with STEREO-A/HI-1 detections into late August. C/2025 R2 (SWAN) is past perihelion, which occurred in mid September 2025. On September 12 this comet will pass within 0.3 AU of the earth. It reached maximum brightness in late September
C/2025 K1 (ATLAS) was discovered on May 24. It is brightening ahead of perihelion in early October, when it might be 7.5 magnitude. The best view will be after perhilion but it is unlikely to survive.
C/2024 E1 (Wierzchos) - will reach perihelion on January 20 2026. It is currently predicted to reach maximum brightness of magnitude 9 in late January.
217P/LINEAR passed perhilion in late May and is fading slowly. It has a 7.8 year orbital period.
C/2021 G2 (ATLAS) is past perihelion, which occurred in early September 2024. It reached maximum brightness of magnitude 14 in late August.
29P/Schwassmann-Wachmann has frequent outbursts, typically resulting in a brightening of 1 - 4.0 magnitudes. 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 continuously. See Mission 29P from the BAA for up to date information.
C/2014 UN271 (Bernardinelli-Bernstein) is an interesting Oort cloud comet that was reported as a result of the Dark Energy Survey. Soon after it was made public, images showed a cometary coma. Discovery credit goes to Pedro Bernardinelli and Gary Bernstein. This is a remarkable comet that was at 29 AU in 2014, with a perihelion of 10.9 AU in 2031. Its orbit extends out to 40,000 AU! It was unusually bright for its distance. HST observations that isolate the nucleus estimate the diameter to be between 120 and 140 km, making this possibly the largest comet nucleus yet measured. Because of its distant perihelion, this comet is not expected to become bright enough to be visually observed except in large instruments, and not until the end of the decade, but it is likely going to be the subject of intense scientific scrutiny.
Comets that have apparently di
sintegrated: C/2025 F2, C/2024 G3, C/2024 S1 (ATLAS), C/2022 S3 (PANSTARRS), C/2021 P4 (ATLAS), C/2020 Q1 (Borisov), C/2020 P1 (NEOWISE), and C/2019 Y4 (ATLAS). Beware that various sources often fail to keep track of whether or not a comet still exists!Comet Visibility in the Eyepiece
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.
This
page uses code developed for SkyTools to predict the visibility of a comet. Predicting how much
aperture is required to see a comet is a very complex task. The magnitude
alone is a very poor predictor. SkyTools considers the magnitude, coma
diameter, and degree of concentration of the comet, based on recent
observations.The predictions are made for a Country/Suburban site,
which is approximately
Bortle
5, unless
indicated otherwise. 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!
Observing
Synopses for October
Explanation
of Comet Synopses and charts (read this if you have questions) C/2025 A6 (Lemmon): An
evening comet visible to the naked eye C/2025 R2 (SWAN): An
evening comet visible in binoculars C/2025 K1 (ATLAS): A
morning comet visible in small telescopes at a dark site, or a 12.5-inch (32 cm)
under a country sky 240P/NEAT: A morning comet
visible in a 12.5-inch (32 cm) telescope at a dark site C/2024 E1 (Wierzchos): An
evening comet visible in an 18-inch (46 cm) telescope at a dark site 210P/Christensen: A
southern hemisphere evening comet visible in a 24-inch telescope at a dark site Summary
Data for This Month's Telescopic Comets
This comet begins the month in Lynx at magnitude 6.9. Look for a
13' coma, condensation is a diffuse spot in coma center; moderately condensed.
It should brighten rapidly, moving into Hercules by month's end. FINDER
CHART
Latitude
Visibility October 4
Visibility October 11
Visibility October 18
Visibility October 25
Visibility November 1
Nights Visible
55o
N
Not visible
Fairly high during morning
twilight at ~04:50
Fairly high in the western sky
during evening twilight at ~18:30
Fairly high in the western sky
during evening twilight at ~18:10
Low in the western sky during
evening twilight at ~17:50
1-
40o
N
Not visible
Fairly high during morning
twilight at ~05:00
Low in the western sky during
evening twilight at ~18:20
Fairly high in the western sky
during evening twilight at ~18:10
Low in the western sky during
evening twilight at ~18:10
1-
Equator
Not visible
Not visible
Not visible
Low in the western sky during
evening twilight at ~18:30
Low in the western sky during
evening twilight at ~18:40
1-13, 22-
30o S
Not visible
Not visible
Not visible
Not visible
Not visible
29-
This comet begins the month in Libra at magnitude 6.4. Look for
a 7.5' coma, condensation is a bright diffuse spot at center of coma. It should
fade rapidly, moving into Aquarius by month's end. FINDER
CHART
Latitude
Visibility October 4
Visibility October 11
Visibility October 18
Visibility October 25
Visibility November 1
Nights Visible
55o
N
Not visible
Very low in the western sky
during evening twilight at ~18:20
Low in the southern sky during
evening twilight at ~18:30
Fairly high in the southern sky
during evening twilight at ~18:20
Fairly high in moonlight at
~18:50
7-
40o
N
Very low in the western sky
during evening twilight at ~18:30
Low in the western sky during
evening twilight at ~18:30
Fairly high in the southern sky
during evening twilight at ~18:40
High at ~19:10
High in moonlight at ~18:30
1-
Equator
Fairly high in the western sky
during evening twilight at ~18:40
Fairly high during evening
twilight at ~18:50
High during evening twilight at
~19:00
High in moonlight at ~19:00
High during evening twilight at
~18:50
1-
30o S
Fairly high in the western sky
during evening twilight at ~19:00
Fairly high during evening
twilight at ~19:20
High during evening twilight at
~19:30
High during evening twilight at
~19:40
High during evening twilight at
~19:40
1-
This comet begins the month in Virgo at magnitude 9.4. Look for
a 1.5' coma, diffuse condensation at center. It should fade by about 1.2
magnitudes by month's end. FINDER
CHART
Latitude
Visibility October 4
Visibility October 11
Visibility October 18
Visibility October 25
Visibility November 1
Nights Visible
55o
N
Not visible
Not visible
Not visible
Low in the eastern sky during
morning twilight at ~05:20
Fairly high in the eastern sky
during morning twilight at ~05:20
19-
40o
N
Not visible
Not visible
Not visible
Low in the eastern sky during
morning twilight at ~05:10
Fairly high in the eastern sky
during morning twilight at ~05:10
17-
Equator
Not visible
Not visible
Not visible
Low in the eastern sky during
morning twilight at ~04:40
Fairly high in the eastern sky
during morning twilight at ~04:40
14-
30o S
Not visible
Not visible
Not visible
Not visible
Not visible
17-
This comet begins the month in Eridanus at magnitude 13.5. Look
for a 1.5' , diffuse coma with definite brightening toward center. It should
brighten by about 0.5 magnitudes, moving into Taurus by month's end. FINDER
CHART
Latitude
Visibility October 4
Visibility October 11
Visibility October 18
Visibility October 25
Visibility November 1
Nights Visible
55o
N
Fairly high at ~03:20
Not visible
Fairly high at ~02:30
Fairly high at ~02:00
Fairly high at ~02:00
1-6, 10-
40o
N
High at ~03:40
Not visible
High at ~02:30
High at ~01:50
High at ~02:20
1-6, 10-
Equator
High at ~04:00
Not visible
High at ~02:30
High at ~01:50
High at ~02:30
1-6, 10-
30o S
High at ~04:10
High at ~00:20
High at ~02:30
High at ~01:50
High at ~02:40
1-7, 9-
This comet begins the month in Hercules at magnitude 14.0. Look
for a 1' coma, diffuse condensation at center. It should brighten by about 0.8
magnitudes by month's end. FINDER
CHART
Latitude
Visibility October 4
Visibility October 11
Visibility October 18
Visibility October 25
Visibility November 1
Nights Visible
55o
N
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 ~18:40
Fairly high in the western sky
during evening twilight at ~18:30
Fairly high in the western sky
during evening twilight at ~18:10
1-
40o
N
High during evening twilight at
~19:00
Fairly high during evening
twilight at ~18:50
Fairly high during evening
twilight at ~18:40
Fairly high in the western sky
during evening twilight at ~18:30
Fairly high in the western sky
during evening twilight at ~18:20
1-
Equator
Not visible
Fairly high during evening
twilight at ~18:50
Fairly high in the western sky
during evening twilight at ~18:50
Fairly high in the western sky
during evening twilight at ~18:50
Not visible
1-
30o S
Not visible
Not visible
Not visible
Not visible
Not visible
1-2, 7-20
This comet begins the month in Corona Australis at magnitude
16.7. Look for a 20" coma, diffuse condensation at center. It should
brighten rapidly, moving into Scorpius by month's end. The best visibility is
late in the month as seen from the southern hemisphere. FINDER
CHART
Latitude
Visibility October 4
Visibility October 11
Visibility October 18
Visibility October 25
Visibility November 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
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 ~18:50
Low in the western sky during
evening twilight at ~18:40
7-
30o S
Not visible
High during evening twilight at
~19:30
High during evening twilight at
~19:30
Fairly high during evening
twilight at ~19:30
Fairly high in the western sky
during evening twilight at
Comets
brighter than 16th 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/2025 R2 (SWAN) | Libra | 6.4 | 4.6' | 6.4 | 8.1' | 8.1 | 6.6' | 2025 October 1 |
| C/2025 A6 (Lemmon) | Lynx | 6.9 | 7.9' | 4.3 | 12.6' | 2.8 | 11.0' | 2025 October 2 |
| C/2025 K1 (ATLAS) | Virgo | 9.4 | 1.1' | 9.2 | 1.1' | 10.6 | 1.6' | 2025 September 25 |
| 3I/ATLAS | Libra | 12.8 | 50" | 12.1 | 51" | 11.6 | 54" | 2025 October 1 |
| 198P/ODAS | Gemini | 13.1 | 1.2' | 12.9 | 1.3' | 12.7 | 1.5' | 2021 November 30 |
| 240P/NEAT | Eridanus | 13.5 | 1.1' | 13.3 | 1.2' | 13.0 | 1.3' | 2025 October 1 |
| 29P/Schwassmann-Wachmann* | Leo | 13.7 | 1.6' | 13.6 | 1.6' | 13.6 | 1.6' | 2025 June 27 |
| C/2024 E1 (Wierzchos) | Hercules | 14.0 | 1.0' | 13.7 | 1.1' | 13.2 | 1.1' | 2025 September 29 |
| C/2022 N2 (PANSTARRS) | Taurus | 14.4 | 1.0' | 14.3 | 1.1' | 14.3 | 1.1' | 2025 September 24 |
| C/2021 G2 (ATLAS) | Serpens Caput | 15.1 | 47" | 15.2 | 46" | 15.3 | 45" | 2025 September 19 |
| C/2023 R1 (PANSTARRS) | Aquila | 15.5 | 31" | 15.5 | 29" | 15.6 | 28" | 2025 August 22 |
| C/2022 E2 (ATLAS) | Andromeda | 15.5 | 45" | 15.6 | 45" | 15.7 | 43" | 2025 August 22 |
| C/2024 J3 (ATLAS) | Scutum | 15.5 | 24" | 15.5 | 23" | 15.5 | 23" | 2025 August 22 |
| C/2022 QE78 (ATLAS) | Cancer | 15.8 | 44" | 15.7 | 45" | 15.6 | 47" | 2025 September 29 |
| C/2024 T5 (ATLAS) | Eridanus | 15.8 | 29" | 15.7 | 30" | 15.6 | 30" | 2025 September 24 |
| 210P/Christensen | Corona Australis | 16.7 | 17" | 15.6 | 18" | 14.1 | 21" | 2025 September 24 |
| 24P/Schaumasse | Gemini | 17.8 | 1.5' | 16.4 | 1.8' | 14.7 | 2.1' | 2025 September 21 |
For information about specific comets see Gary W. Kronk's Cometography
Make your own visual observing custom charts for your location and telescope/binoculars: Software for visual comet observing
Select comets that are appropriate for your
imaging system, and plan when they are best imaged: Software
for comet imaging
| Links
Skyhound's Guide
to Comets
|