Comet C/2025 A6 (Lemmon) is forecast to reach the brightest point in its 2025 apparition on 3 November. At that time, it will lie at a distance of 0.54 AU from the Sun, and at a distance of 0.86 AU from the Earth.
From South El Monte on 3 November it will become visible at around 17:23 (PDT), 25° above your western horizon, as dusk fades to darkness. It will then sink towards the horizon, setting 2 hours and 37 minutes after the Sun at 19:33.
The events that comprise the 2025 apparition of C/2025 A6 (Lemmon) are as follows:
Date | Event |
21 Oct 2025 | Comet C/2025 A6 (Lemmon) passes perigee |
03 Nov 2025 | Comet C/2025 A6 (Lemmon) reaches peak brightness |
08 Nov 2025 | Comet C/2025 A6 (Lemmon) passes perihelion |
The table below lists the times when C/2025 A6 (Lemmon) will be visible from South El Monte day-by-day through its apparition:
Date | Constellation | Comet visibility |
13 Oct 2025 | Canes Venatici | Visible from 04:36 until 06:14 Highest at 06:14, 29° above NE horizon |
15 Oct 2025 | Canes Venatici | Visible from 05:06 until 06:19 Highest at 06:19, 24° above NE horizon |
17 Oct 2025 | Canes Venatici | Visible from 18:47 until 19:16 05:41 until 06:24 Highest at 06:24, 19° above NE horizon |
19 Oct 2025 | Canes Venatici | Visible from 18:41 until 19:36 06:19 until 06:28 Highest at 18:41, 20° above NW horizon |
21 Oct 2025 | Bootes | Visible from 18:36 until 19:50 Highest at 18:36, 24° above W horizon |
23 Oct 2025 | Bootes | Visible from 18:32 until 20:00 Highest at 18:32, 27° above W horizon |
25 Oct 2025 | Serpens Caput | Visible from 18:27 until 20:05 Highest at 18:27, 29° above W horizon |
27 Oct 2025 | Serpens Caput | Visible from 18:23 until 20:07 Highest at 18:23, 30° above W horizon |
29 Oct 2025 | Serpens Caput | Visible from 18:19 until 20:06 Highest at 18:19, 30° above W horizon |
31 Oct 2025 | Ophiuchus | Visible from 18:15 until 20:02 Highest at 18:15, 30° above W horizon |
02 Nov 2025 | Ophiuchus | Visible from 17:13 until 18:55 Highest at 17:13, 28° above SW horizon |
04 Nov 2025 | Ophiuchus | Visible from 17:12 until 18:47 Highest at 17:12, 27° above SW horizon |
06 Nov 2025 | Ophiuchus | Visible from 17:10 until 18:38 Highest at 17:10, 25° above SW horizon |
08 Nov 2025 | Ophiuchus | Visible from 17:08 until 18:28 Highest at 17:08, 23° above SW horizon |
10 Nov 2025 | Ophiuchus | Visible from 17:07 until 18:17 Highest at 17:07, 21° above SW horizon |
12 Nov 2025 | Ophiuchus | Visible from 17:06 until 18:05 Highest at 17:06, 19° above SW horizon |
14 Nov 2025 | Ophiuchus | Visible from 17:07 until 17:51 Highest at 17:07, 16° above SW horizon |
16 Nov 2025 | Ophiuchus | Visible from 17:09 until 17:35 Highest at 17:09, 14° above SW horizon |
18 Nov 2025 | Ophiuchus | Visible from 17:11 until 17:19 Highest at 17:11, 11° above SW horizon |
20 Nov 2025 | Ophiuchus | Not observable |
22 Nov 2025 | Ophiuchus | Not observable |
A more detailed table of C/2025 A6 (Lemmon)'s position on each night is available here. A diagram of the orbit of C/2025 A6 (Lemmon) is available here.
Finder chart
The chart below shows the path of C/2025 A6 (Lemmon) over the course of its apparition, as calculated from the orbital elements published by the Minor Planet Center (MPC). It is available for download, either on dark background, in PNG, PDF or SVG formats, or on a light background, in PNG, PDF or SVG formats. It was produced using StarCharter.
Comet brightnesses
Comets are intrinsically highly unpredictable objects, since their brightness depends on the scattering of sunlight from dust particles in the comet's coma and tail. This dust is continually streaming away from the comet's nucleus, and its density at any particular time is governed by the rate of sublimation of the ice in the comet's nucleus, as it is heated by the Sun's rays. It also depends on the amount of dust that is mixed in with that ice. This is very difficult to predict in advance, and can be highly variable even between successive apparitions of the same comet.
In consequence, while the future positions of comets are usually known with a high degree of confidence, their future brightnesses are not. For most comets, we do not publish any magnitude estimates at all. For the few comets where we do make estimates, we generally prefer the BAA's magnitude parameters to those published by the Minor Planet Center, since they are typically updated more often.
Based on the magnitude parameters published for this comet by the BAA Comet Section, we estimate that it may be around mag 0 on 3 November 2025. This estimate is based on observations that the BAA has received from amateur astronomers, assuming that its current level of activity will remain constant.
The comet's position on 3 November 2025 will be:
Object | Right Ascension | Declination | Constellation | Magnitude |
Comet C/2025 A6 (Lemmon) | 16h37m30s | 1°57'S | Ophiuchus | 0.1 |
The coordinates are given in J2000.0.
The sky on 3 Nov 2025
The sky on 3 November 2025 | ||||||||||||||||||||||||||||||||||
97% 13 days old |
All times shown in PST.
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Source
This event was automatically generated on the basis of orbital elements published by the Minor Planet Center (MPC) , and is updated whenever new elements become available. It was last updated on 01 Oct 2025.
Image credit
© Andy Roberts 1997. Pictured comet is C/1995 O1 Hale-Bopp.