Comet Chasing in December
Comet chasing is the visual observation of telescopic comets. Jump to: Observing synopses Summary data Buy me a Coffee
We have a remarkable five comets visible in small telescopes 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 the 3rd interstellar comet. It is currently magnitude 10.8. It passed closest to the sun on October 29 at a distance of 1.4 AU. See below for information about observing it in the telescope.
C/2025 A6 (Lemmon) - is an amazing comet that brightened quickly in late August and became a naked eye object in October and November. There were reports of fans, streamers, and other structures apparent in the eyepiece at high magnification. This comet is hidden in the glare of the sun this month.
C/2025 T1 (ATLAS) will reach perihelion in early December. It reached maximum brightness of magnitude 11.2 in mid November. This is currently the best comet to observe with small telescopes.
24P/Schuamasse is a peridoc comet with an 8.2 year orbital period. Perhihelion is on January 8, 2026. It is predicted to reach maximum brightness of magnitude 11.3 in early January.
C/2025 K1 (ATLAS) has fragmented, splitting into at least three parts (November 10). Fragmentation is ongoing, with some appearing and others disappearing. This comet was discovered on May 24 and is currently magnitude 10.1. It passed perihelion on October 8, and is now gracing our morning skies.
240P/NEAT is a periodic comet with a 7.6 year orbital period. Perihelion is on December 19. It is predicted to reach maximum brightness of magnitude 13 in early December.
210P/Christensen is a periodic comet with a 5.6 year orbital period. Perihelion is on November 22, when it will also be within 0.5 AU of the earth.
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 passed within 0.3 AU of the earth. It reached maximum brightness in late September
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.
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 December
Explanation
of Comet Synopses and charts (read this if you have questions) C/2025 T1 (ATLAS): A
northern hemisphere evening comet visible in small telescopes 24P/Schaumasse: A morning
comet visible in small telescopes at a dark site, or a 6-inch (15 cm) under a
country sky 3I/ATLAS: A morning comet
visible in small telescopes at a dark site, or a 6-inch (15 cm) under a country
sky C/2025 K1 (ATLAS): A
morning comet visible in small telescopes at a dark site, or a 10-inch (25 cm)
under a country sky 240P/NEAT: An evening
comet visible in a 6-inch (15 cm) telescope at a dark site, or a 14-inch (36 cm)
under a country sky 210P/Christensen: A
morning comet visible in an 8-inch (20 cm) telescope at a dark site C/2025 R2 (SWAN): An
evening comet visible in an 8-inch (20 cm) telescope at a dark site, or a
24-inch telescope under a country sky 235P/LINEAR: A morning
comet visible in a 12.5-inch (32 cm) telescope at a dark site C/2022 N2 (PANSTARRS): An
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 Vulpecula at magnitude 9.6. Look
for a 3' coma, diffuse condensation at center. It should fade rapidly, moving
into Aquila by month's end. FINDER
CHART
Latitude
Visibility November 29
Visibility December 6
Visibility December 13
Visibility December 20
Visibility December 27
Nights Visible
55o
N
High during evening twilight at
~17:40
Fairly high during evening
twilight at ~17:30
Fairly high during evening
twilight at ~17:40
Fairly high in the western sky
during evening twilight at ~17:40
Fairly high in the western sky
during evening twilight at ~17:40
1-
40o
N
High during evening twilight at
~18:00
Fairly high during evening
twilight at ~18:00
Fairly high during evening
twilight at ~18:00
Fairly high in the western sky
during evening twilight at ~18:00
Fairly high in the western sky
during evening twilight at ~18:10
1-
Equator
Fairly high in the western sky
during evening twilight at ~18:50
Fairly high in the western sky
during evening twilight at ~19:00
Fairly high in the western sky
during evening twilight at ~19:00
Low in the western sky during
evening twilight at ~19:00
Not visible
1-
30o S
Not visible
Not visible
Not visible
Not visible
Not visible
This comet begins the month in Leo at magnitude 11.7. Look for a
2' , diffuse coma with definite brightening toward center. It should brighten by
about 1.3 magnitudes, moving into Coma Berenices by month's end. FINDER
CHART
Latitude
Visibility November 29
Visibility December 6
Visibility December 13
Visibility December 20
Visibility December 27
Nights Visible
55o
N
High at ~05:40
High during morning twilight at
~06:00
High in moonlight at ~05:50
High at ~06:00
High at ~06:10
1-
40o
N
High at ~05:20
High during morning twilight at
~05:40
High in moonlight at ~05:30
High during morning twilight at
~05:50
High during morning twilight at
~05:50
1-
Equator
High during morning twilight at
~04:30
Not visible
High during morning twilight at
~04:40
High during morning twilight at
~04:40
High during morning twilight at
~04:50
1-
30o S
Not visible
Not visible
Fairly high during morning
twilight at ~03:30
Fairly high during morning
twilight at ~03:30
Fairly high during morning
twilight at ~03:40
1-
This comet begins the month in Virgo at magnitude 10.8. Look for
a 2' coma, condensation is a diffuse spot in coma center; moderately condensed.
It should fade rapidly, moving into Leo by month's end. FINDER
CHART
Latitude
Visibility November 29
Visibility December 6
Visibility December 13
Visibility December 20
Visibility December 27
Nights Visible
55o
N
Fairly high during morning
twilight at ~06:00
Fairly high during morning
twilight at ~06:00
Fairly high in moonlight at
~05:40
High at ~04:40
Not visible
1-
40o
N
High during morning twilight at
~05:30
High during morning twilight at
~05:40
High in moonlight at ~05:30
High at ~04:40
High at ~03:30
1-
Equator
High during morning twilight at
~04:40
High during morning twilight at
~04:40
High during morning twilight at
~04:40
High at ~04:30
High at ~03:30
1-
30o S
Fairly high in the eastern sky
during morning twilight at ~03:30
Fairly high during morning
twilight at ~03:30
High during morning twilight at
~03:30
High during morning twilight at
~03:30
Not visible
1-
This comet begins the month in Camelopardalis at magnitude 11.0.
Look for a 3' coma, condensation is a diffuse spot in coma center; moderately
condensed. It should fade rapidly, moving into Andromeda by month's end. FINDER
CHART
Latitude
Visibility November 29
Visibility December 6
Visibility December 13
Visibility December 20
Visibility December 27
Nights Visible
55o
N
High at ~01:20
High during evening twilight at
~17:30
High at ~19:30
Not visible
Not visible
1-29
40o
N
High at ~01:10
High at ~18:20
High at ~19:40
Not visible
Not visible
1-29
Equator
Not visible
Fairly high in the northern sky
at ~20:10
Not visible
Not visible
Not visible
1-29
30o S
Not visible
Not visible
Not visible
Not visible
Not visible
10-28
This comet begins the month in Taurus at magnitude 12.3. Look
for a 60" , diffuse coma with definite brightening toward center. It should
fade slowly, moving into Aries by month's end. FINDER
CHART
Latitude
Visibility November 29
Visibility December 6
Visibility December 13
Visibility December 20
Visibility December 27
Nights Visible
55o
N
Fairly high at ~00:40
Fairly high in moonlight at
~20:20
High at ~22:00
High at ~21:30
High in moonlight at ~21:30
1-
40o
N
High at ~01:00
Fairly high at ~18:50
High at ~22:00
High at ~21:20
High in moonlight at ~21:40
1-
Equator
High at ~01:00
High at ~20:00
High at ~22:00
High at ~21:20
High in moonlight at ~21:40
1-
30o S
High at ~00:50
High at ~21:10
High at ~22:00
High at ~21:20
High in moonlight at ~21:10
1-
This comet begins the month in Virgo at magnitude 11.3. Look for
a 55" coma, diffuse condensation at center. It should fade rapidly, moving
into Libra by month's end. FINDER
CHART
Latitude
Visibility November 29
Visibility December 6
Visibility December 13
Visibility December 20
Visibility December 27
Nights Visible
55o
N
Not visible
Not visible
Not visible
Not visible
Not visible
1-30
40o
N
Low in the eastern sky during
morning twilight at ~05:40
Low in the eastern sky during
morning twilight at ~05:50
Not visible
Not visible
Not visible
1-
Equator
Low in the eastern sky during
morning twilight at ~04:50
Fairly high in the eastern sky
during morning twilight at ~04:50
Not visible
Not visible
Not visible
1-
30o S
Not visible
Not visible
Not visible
Not visible
Not visible
1-29
This comet begins the month in Pisces at magnitude 11.2. Look
for a 2.5' coma, center much brighter than edges, though still diffuse. It
should fade rapidly. FINDER
CHART
Latitude
Visibility November 29
Visibility December 6
Visibility December 13
Visibility December 20
Visibility December 27
Nights Visible
55o
N
High in moonlight at ~18:20
High during evening twilight at
~17:40
High at ~19:00
High at ~18:50
Not visible
1-29
40o
N
High in moonlight at ~18:10
High at ~18:20
High at ~19:00
High at ~18:50
Not visible
1-29
Equator
High during evening twilight at
~19:00
High at ~19:20
High at ~19:20
High at ~19:20
Not visible
1-29
30o S
High during evening twilight at
~20:20
High during evening twilight at
~20:20
High during evening twilight at
~20:30
High during evening twilight at
~20:30
Not visible
1-
This comet begins the month in Virgo at magnitude 13.5. Look for
a 55" coma, diffuse condensation at center. It should brighten slowly,
moving into Libra by month's end. FINDER
CHART
Latitude
Visibility November 29
Visibility December 6
Visibility December 13
Visibility December 20
Visibility December 27
Nights Visible
55o
N
Not visible
Not visible
Not visible
Not visible
Not visible
1-
40o
N
Not visible
Fairly high in the eastern sky
during morning twilight at ~05:40
Fairly high in the southern sky
during morning twilight at ~05:50
Fairly high in the southern sky
during morning twilight at ~05:50
Fairly high in the southern sky
during morning twilight at ~05:50
1-
Equator
Fairly high in the eastern sky
during morning twilight at ~04:40
Fairly high during morning
twilight at ~04:40
Fairly high during morning
twilight at ~04:40
Fairly high during morning
twilight at ~04:50
High during morning twilight at
~04:50
1-
30o S
Not visible
Not visible
Fairly high in the eastern sky
during morning twilight at ~03:30
Fairly high in the eastern sky
during morning twilight at ~03:40
Fairly high in the eastern sky
during morning twilight at ~03:40
1-
This comet begins the month in Aries at magnitude 14.0. Look for
a 1' coma, center much brighter than edges, though still diffuse. It should fade
slowly. FINDER CHART
Latitude
Visibility November 29
Visibility December 6
Visibility December 13
Visibility December 20
Visibility December 27
Nights Visible
55o
N
High at ~01:00
Fairly high during evening
twilight at ~17:50
High at ~21:40
High at ~21:10
High in moonlight at ~22:20
1-2, 6-29
40o
N
High at ~01:00
High at ~18:30
High at ~21:40
High at ~21:10
High in moonlight at ~23:20
1-2, 5-29
Equator
High at ~01:00
High at ~20:00
High at ~21:40
High at ~21:10
High in moonlight at ~21:20
1-2, 5-29
30o S
Fairly high in moonlight at
~23:20
Fairly high at ~21:20
Fairly high at ~21:40
Fairly high at ~21:20
Fairly high in moonlight at
~21:00
1-1, 5-29
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 |
December 1st |
December 15th |
December 31st |
Observations as of (UT) | |||
| Mag | Diam | Mag | Diam | Mag | Diam | |||
| C/2025 A6 (Lemmon)* | Ophiuchus | 7.0 | 3.0' | 8.3 | 2.6' | 9.5 | 2.5' | 2025 November 21 |
| C/2025 T1 (ATLAS) | Vulpecula | 9.6 | 3.1' | 10.3 | 2.5' | 11.5 | 2.0' | 2025 November 27 |
| 3I/ATLAS | Virgo | 10.8 | 2.2' | 11.7 | 2.3' | 12.8 | 2.2' | 2025 November 28 |
| C/2025 K1 (ATLAS) | Camelopardalis | 11.0 | 3.1' | 12.8 | 1.8' | 14.5 | 1.1' | 2025 November 28 |
| C/2025 R2 (SWAN) | Pisces | 11.2 | 2.8' | 12.3 | 2.1' | 13.4 | 1.6' | 2025 November 20 |
| 210P/Christensen | Virgo | 11.3 | 57" | 13.6 | 42" | 16.0 | 35" | 2025 November 26 |
| 24P/Schaumasse | Leo | 11.7 | 1.7' | 10.9 | 1.8' | 10.4 | 1.9' | 2025 November 26 |
| C/2024 E1 (Wierzchos) | Ophiuchus | 11.9 | 1.2' | 11.2 | 1.3' | 10.2 | 1.5' | 2025 November 21 |
| 198P/ODAS | Taurus | 12.1 | 2.0' | 12.1 | 2.0' | 12.3 | 1.9' | 2021 November 30 |
| 240P/NEAT | Taurus | 12.3 | 59" | 12.4 | 57" | 12.6 | 52" | 2025 November 27 |
| 235P/LINEAR | Virgo | 13.5 | 48" | 13.4 | 51" | 13.3 | 54" | 2025 November 20 |
| C/2022 N2 (PANSTARRS) | Aries | 14.0 | 1.1' | 14.1 | 1.0' | 14.3 | 58" | 2025 November 26 |
| C/2025 V1 (Borisov) | Ophiuchus | 14.7 | 47" | 16.9 | 34" | 18.7 | 27" | 2025 November 25 |
| C/2024 T5 (ATLAS) | Eridanus | 15.3 | 31" | 15.3 | 30" | 15.2 | 30" | 2025 November 25 |
| C/2021 G2 (ATLAS) | Ophiuchus | 15.4 | 44" | 15.5 | 44" | 15.5 | 44" | 2025 October 25 |
| C/2022 QE78 (ATLAS) | Leo | 15.4 | 52" | 15.4 | 54" | 15.3 | 55" | 2025 November 23 |
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
|