© Andy Roberts 1997. Pictured comet is C/1995 O1 Hale-Bopp.

Comet C/2023 H2 (Lemmon) passes perigee

Dominic Ford, Editor
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Comet C/2023 H2 (Lemmon) will make its closest approach to the Earth on 10 November, at a distance of of 0.19 AU.

From San Diego on the day of perigee it will become visible at around 17:50 (PST), 49° above your western horizon, as dusk fades to darkness. It will then sink towards the horizon, setting at 21:59.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

The events that comprise the 2023 apparition of C/2023 H2 (Lemmon) are as follows:

Date Event
29 Oct 2023Comet C/2023 H2 (Lemmon) passes perihelion
10 Nov 2023Comet C/2023 H2 (Lemmon) passes perigee
10 Nov 2023Comet C/2023 H2 (Lemmon) reaches peak brightness

The table below lists the times when C/2023 H2 (Lemmon) will be visible from San Diego day-by-day through its apparition:

Date Constellation Comet visibility
20 Oct 2023Canes VenaticiVisible from 05:21 until 05:55
Highest at 05:55, 27° above NE horizon
22 Oct 2023Canes VenaticiVisible from 05:20 until 05:56
Highest at 05:56, 27° above NE horizon
24 Oct 2023Canes VenaticiVisible from 05:21 until 05:58
Highest at 05:58, 27° above NE horizon
26 Oct 2023Canes VenaticiVisible from 05:25 until 05:59
Highest at 05:59, 27° above NE horizon
28 Oct 2023Canes VenaticiVisible from 05:33 until 06:01
Highest at 06:01, 26° above NE horizon
30 Oct 2023Ursa MajorVisible from 05:47 until 06:02
Highest at 06:02, 24° above NE horizon
01 Nov 2023BootesNot observable
03 Nov 2023BootesVisible from 18:55 until 19:12
Highest at 18:55, 24° above NW horizon
05 Nov 2023HerculesVisible from 17:54 until 18:49
Highest at 17:54, 31° above NW horizon
07 Nov 2023HerculesVisible from 17:52 until 19:29
Highest at 17:52, 40° above NW horizon
09 Nov 2023HerculesVisible from 17:51 until 20:03
Highest at 17:51, 49° above W horizon
11 Nov 2023AquilaVisible from 17:50 until 20:19
Highest at 17:50, 52° above SW horizon
13 Nov 2023AquilaVisible from 17:49 until 20:17
Highest at 17:49, 47° above SW horizon
15 Nov 2023CapricornusVisible from 17:48 until 20:06
Highest at 17:48, 40° above S horizon
17 Nov 2023CapricornusVisible from 17:47 until 19:50
Highest at 17:47, 34° above S horizon
19 Nov 2023CapricornusVisible from 17:46 until 19:31
Highest at 17:46, 30° above S horizon
21 Nov 2023Piscis AustrinusVisible from 17:45 until 19:10
Highest at 17:45, 27° above S horizon
23 Nov 2023Piscis AustrinusVisible from 17:45 until 18:45
Highest at 17:45, 25° above S horizon
25 Nov 2023Piscis AustrinusVisible from 17:44 until 18:12
Highest at 17:44, 23° above S horizon
27 Nov 2023Piscis AustrinusNot observable
29 Nov 2023GrusNot observable

A more detailed table of C/2023 H2 (Lemmon)'s position on each night is available here. A diagram of the orbit of C/2023 H2 (Lemmon) is available here.

Finder chart

The chart below shows the path of C/2023 H2 (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 7 on 10 November 2023. This estimate is based on observations that the BAA has received from amateur astronomers, assuming that its current level of activity will remain constant.

This comet is not expected to be visible to the naked eye, but might be visible through bird-watching binoculars.

The comet's position at perigee will be:

Object Right Ascension Declination Constellation Magnitude
Comet C/2023 H2 (Lemmon) 18h25m10s 22°36'N Hercules 6.7

The coordinates are given in J2000.0.

The sky on 10 Nov 2023

The sky on 10 November 2023
Twilight ends
Twilight begins

27-day old moon
Waning Crescent


27 days old

Rise Culm. Set
Mercury 07:18 12:21 17:25
Venus 02:37 08:40 14:44
Moon 03:33 09:32 15:23
Mars 06:24 11:40 16:55
Jupiter 16:19 22:56 05:34
Saturn 13:11 18:40 00:09
All times shown in PST.


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 02 Dec 2023.

Image credit

© Andy Roberts 1997. Pictured comet is C/1995 O1 Hale-Bopp.


San Diego



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