A new ‘green’ comet for 2023

There’s a new comet in the sky which is already creating a flurry of interest among amateur astronomers, visible at the end of January and early February 2023. Don’t get your hopes up too high, but just be pleasantly surprised if you manage to spot it with binoculars.But don’t expect to see it looking green as the media hype says!

Updated 14 February 2023

The comet is called C/2022 E3 ZTF, and it gets this jolly name from the time it was discovered and the instrument used to locate it. It is still visible using binoculars in the evening sky, but unless you have very dark skies the view is less than impressive and people just report seeing a faint circular glow.

Photographs (see below) show it with a green centre, which is quite common in comets due to the molecule cyanogen, (CN)2. However, even with a large telescope you are unlikely to see the colour. That’s the way it is, but the clickbait stories won’t tell you that.

Observers equipped with even small telescopes and cameras (and good tracking mounts) are still able to take pictures of the comet, which will reveal something of its green colour and maybe a faint tail. You will need a chart to be able to find it, but it’s currently about magnitude 7. 

The comet was at its closest to Earth on 2 February when it was 48.5 million km from Earth.. Here are positions calculated by Chris Marriott’s SkyMap software for midnight (0 hours) on the dates shown. The distance shown is the distance from the Earth in astronomical units (the Earth–Sun distance) where 1 AU = 149,600,000 km. 

Many news stories are saying that the comet was last seen during the Neolithic period. However, the orbital details don’t confirm this, and show it having a nearly parabolic orbit. The best we can say is that its period is indeterminate.

Ephemeris of comet C/2022 E3 ZTF

Date Top R.A. Top Dec Mag Distance
14 Feb 2023 04h 44m 33.6s +18° 31′ 34″ 6.9 0.4961
15 Feb 2023 04h 43m 26.1s +16° 29′ 07″ 7.0 0.5235
16 Feb 2023 04h 42m 30.3s +14° 39′ 05″ 7.2 0.5515
17 Feb 2023 04h 41m 44.2s +12° 59′ 55″ 7.3 0.5800
18 Feb 2023 04h 41m 06.5s +11° 30′ 12″ 7.4 0.6088
19 Feb 2023 04h 40m 35.8s +10° 08′ 48″ 7.5 0.6380
20 Feb 2023 04h 40m 11.2s +08° 54′ 41″ 7.7 0.6674
21 Feb 2023 04h 39m 52.1s +07° 46′ 59″ 7.8 0.6970
22 Feb 2023 04h 39m 37.6s +06° 44′ 57″ 7.9 0.7268
23 Feb 2023 04h 39m 27.4s +05° 47′ 57″ 8.0 0.7567
24 Feb 2023 04h 39m 20.9s +04° 55′ 25″ 8.1 0.7868
25 Feb 2023 04h 39m 17.7s +04° 06′ 51″ 8.2 0.8169
26 Feb 2023 04h 39m 17.5s +03° 21′ 52″ 8.3 0.8471
27 Feb 2023 04h 39m 20.1s +02° 40′ 04″ 8.4 0.8773
28 Feb 2023 04h 39m 25.1s +02° 01′ 10″ 8.6 0.9075


Comet C/2022 E3 ZTF, photographed by Brian O’Halloran from Dunabrattin, Co. Waterford on 2 January 2023 at 05:23 UT. He used a Canon 250D camera and 81 mm refractor and a total exposure time of 30 minutes.
Comet C/2022 E3 ZTF, photographed with 72 mm refractor. A combination of 10 30-second exposures from Flackwell Heath, Bucks, by Robin Scagell. The stars are trailed as a result of the comet’s motion. North is to the left. The comet was visible with 10 x 30 binoculars.

Shown below are finder charts for the comet. Bear in mind that if you are observing before midnight, the comet will be close to the position for midnight on the following date.

View taken at 05:00 on 15 January by Jan Drozd using a 114 mm eVscope reflecting telescope.
The comet as photographed from near High Wycombe using a 432 mm focal length lens on 27 January 2023


Comet C/2022 E3 (ZTF). 14 February 2023, 23:55 UT. 150 mm RC reflector, 5 x 30 sec exposures ISO 2500. Sony A7S. Robin Scagell. Flackwell Heath.


Track of the comet looking east during January and February 2023. The curved line indicates the horizon. Stars are shown to magnitude 6. Maps made using Chris Marriott’s SkyMap. Click to enlarge.

Track of C/2022 E3 from 14 to 27 February. Magnitudes shown are approximate. The circle at the top of the track shows a 5° field of view, typical of binoculars. Stars shown to magnitude 8. Map compiled using Chris Marriott’s SkyMap. Click to enlarge