Last year's "Green Comet": C/2022 E3 (ZTF)

A comet designated "C/2022 E3 (ZTF)" was the third comet discovered in 2022.  It was picked up by the Zwicky Transient Facility (ZTF) at Palomar Observatory, a 48-inch Schmidt camera with a 605 Megapixel sensor array.  The comet made its closest approach to the sun on 12 January 2023 and it passed closest to Earth on 1 February 2023.  

Because of the possibility that it would achieve naked-eye visibility it was much hyped as the "Green Comet" in both the mainstream and astronomy press.  It reached a maximum brightness of about magnitude 5 - an easy target with binoculars but just barely visible to the naked eye at a dark-sky site.  The green color is a result of molecular de-excitation of diatomic carbon and cyanogen and is a common feature of most comets.

On any given night there are usually anywhere from six to a dozen comets within visible reach of small telescopes or astro cameras.  According to the Sky Safari app there are eight comets tonight (24 Jan) that could easily be photographed with my usual 135mm f/2 astrophotography lens. Other than flirting with naked-eye visibility, the so-called Green Comet was not unusual or particularly remarkable, in spite of all the hype.

All of the photographs below were obtained from my backyard in urban Santa Fe.

21 January 2023. 2° FOV.  E-M5iii + Rokinon 135mm f/2, ISO 800, 30 s.

As the comet neared Earth its motion was easy to detect over brief time intervals.  The two images in the animation below were obtained 54 minutes apart.  The sky brightness at the time was sqml=19.58.

26 January 2023. 2° FOV.  E-M5iii + Rokinon 135mm f/2.  ISO 800, 40 s.

27 January 2023. 2° FOV.  E-M5iii + Rokinon 135mm f/2.  ISO 800, 40 s.

At the time of closest approach the comet's motion was easy to detect.  The images in the animation below were obtained at approximately 1-minute intervals.  The sky was bright (sqml=15.2) with a 10.7-d waxing gibbous moon.  The comet was high in the northern sky in the constellation Camelopardalis.

31 January 2023. 1° field width.  E-M5iii + Orion 80mmED f/7.5.  ISO 1600, 30 s.

On 10 February the comet was on its way out.  Here it is passing through the line-of-sight near the overexposed planet Mars.

10 February 2023. 4° FOV.  E-M5iii + Olympus 75mm f/1.8.  ISO 1600, 30 s.