Comet C/2022 E3 ZTF

Partial Success

Almost all comets I've been able to observe have been difficult targets. They usually appear inconveniently close to the horizon, often before dawn when it's hard to get out of bed. Recently, prominent comet C/2022 E3 (ZTF) had an orbit bringing it close to the north celestial pole, so, for a good stretch of days, the comet was located relatively high in the sky to the north.

The comet's unfamiliar name has the following explanation according to earthsky.org: "It was discovered on March 2, 2022 and it was the third such object discovered in the fifth half month (A, B, C, D, E) of the year". (E3) It was discovered by a 48-inch telescope on Mount Palomar which is part of the Zwicky Transient Facility (ZTF). The C indicates it is a non-periodic comet.

I made several attempts to photograph the comet with my new Nikon Z6 2 camera. The first attempt on January 15th was successful as you can see in the following image which was constructed by stacking five 30-second guided exposures with a 70 mm f/2.8 lens at ISO 800.

The green coma and brighter part of the yellow dust tail are visible. Ultraviolet light from the Sun excites diatomic carbon present in gases emitted by the comet. The excited diatomic carbon then emits a green visible color. The dust tail's yellow color comes from reflected yellow sunlight. Darker skies, larger apertures, longer exposures, and telescopic magnification would be needed to reveal the long, dim, wispy ion tail which is not visible above.

I tried again on January 24th when the comet was closer to Earth. The next image is a stack of six 6-second unguided exposures at ISO 6400 with the 70 mm lens set at f/2.8.

Now the comet tail had spread out into a fan shape with a spike pointing ahead of the coma. This is a little easier to see in the following heavily enhanced, cropped image. Enhancing the image to reveal dim details also, unfortunately, brightens background noise. Therefore, the background sky doesn't look as black as it should. (All these images should be enlarged to see the comet in better detail.)

Viewing conditions were much more difficult on January 30th, two days before the comet made its closest approach to Earth. On this night the temperature was wonderfully mild, but the Moon was almost full, and the sky was covered with hazy thin clouds. In addition, it was very humid, and dew rapidly formed on exposed surfaces. Since the comet was closer to the celestial pole this night, I tried a slightly longer exposure time with the unguided camera mounted on an ordinary stationary tripod. The next image is a stack of nineteen 8-second exposures at ISO 6400 with the 70 mm lens at f/2.8.

Unfortunately, haze and moonlight worked together to diminish what should have been a brighter coma and possibly longer dim tail. 

The sky was completely overcast when the comet came closest to Earth on February 1st. After February 1st there were a few more opportunities for interesting comet pictures. For example, on February 6th the comet passed close to the bright star, Capella, in the constellation, Auriga. The Moon was nearly full that night when I tried imaging the comet with a 12-inch Dobsonian telescope. Unfortunately, I couldn't find the comet in the telescope's relatively small field of view. On February 10th the dimming comet passed close to Mars, but the sky was cloudy again. Clouds were forecast for almost every night after February 10th. The comet will rapidly dim as it recedes from the Sun and Earth and travels out into the solar system.