The Big Green Comet (2022-E3(ZTF))

Comet 2022-E3(ZTF) (a.k.a. The Big Green Comet) captured from Colorado Springs, Colorado with Big Zeus on 22 January 2023

Fun facts

C/2022 E3 (ZTF) is a long-period comet from the Oort cloud. Astronomers Bryce Bolin and Frank Masci discovered C/2022 E3 (ZTF) using the Zwicky Transient Facility (ZTF) survey, which uses the 1.2-m f/2.4 Schmidt telescope at Palomar Observatory, on 2 March 2022. Upon discovery, the comet had an apparent magnitude of 17.3 and was about 4.3 AU (640 million km; 400 million mi) from the Sun.

The object was initially identified as an asteroid, but subsequent observations revealed it had a very condensed coma, indicating it is a comet. H. Sato reported its coma was 8 arcseconds across in stacked photos he obtained from the remote observatory in Mayhill, New Mexico, while K. Yoshimoto reported its coma was 15 arcseconds across and the comet had a small tail 25 arcseconds long.

The comet was subsequently detected in images taken by Pan-STARRS 1 in Haleakalā Observatory, Hawai’i on 10 July 2021, when the comet had an apparent magnitude of 23. The comet had also been photographed without being noticed by ZTF in October and November 2021.

The comet has a bright green glow around its nucleus, due to the effect of sunlight on diatomic carbon and cyanogen. The comet’s systematic designation starts with C to indicate that it is not a periodic comet, and “2022 E3” means that it was the third comet to be discovered in the first half of March 2022.

The comet nucleus was estimated to be about a kilometer in size, rotating every 8.5 to 8.7 hours. Its tails of dust and gas extended for millions of kilometers and, during January 2023, an anti-tail was also visible.

The comet reached its perihelion on 12 January 2023, at a distance of 1.11 AU (166 million km; 103 million mi), and the closest approach to Earth was on 1 February 2023, at a distance of 0.28 AU (42 million km; 26 million mi). The comet reached magnitude 5 and was visible with the naked eye under moonless dark skies.

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Imaging stream: Orion 10″ f/8 Ritchey-Chretien Astrograph Telescope, Canon EOS Ra
Mount: Sky-Watcher EQ6-R Pro Equatorial Mount (controlled by EQMOD)
Autoguider: Orion 60mm Multi-Use Guide Scope, Orion StarShoot AutoGuider Pro Mono Astrophotography Camera (Controlled by PHD2)

Equipment controlled by HP Probook running Sequence Generator Pro v3.2.0.660

Capture & processing notes

Captured Comet 2022-E3(ZTF) from the HCH front patio on 22 January 2023. Used the capture techniques described by Martin’s Astrophotography in his YouTube video: Tracking a Comet using EQMOD ( Processed using the techniques described in LuckyBudd’s YouTube video: How To Process A Comet With Round Stars using Astropixel Processor, Starnet++ and Photoshop (

Sequence Plan: ISO1600, 58×60 seconds; 22Jan2023, 0447MST – 0613MST

Capture: 22 January 2023, 0447MST – 0613MST
Shooting location: Colorado Springs, Colorado
Processing: Processed with APP, Starnet++, LR/PS