Eight years passed since the night I imaged the Coma Cluster for the first time. It was 6 inches then, and 10 inches now. It was 200 minutes then, and 600 minutes now. The sky is a little bit worse now, but still, I was able to reach much deeper during this attempt.

Coma Cluster is an interesting imaging target for medium and large setups because in the relatively small field of view the vast majority of captured objects are galaxies. And as is usual for clusters of this richness, the galaxies are mostly elliptical, so without any visible features. For this reason, the most important factors for imaging this area are local light pollution and sky transparency. My imaging location is not even close to being a dark place, so all I could do is to wait for a transparent night (or nights) and collect a reasonably large amount of data. I have made this year’s attempt already during four nights in the middle of May, but it took me then quite long to sit down and process this data.

Coma Cluster (Abell 1656)
Coma Cluster (Abell 1656)

The image above is a processed stack of 300 subframes, and each subframe has been exposed for 2 minutes. There are two superhuge elliptical galaxies just above the image center – NGC4889 and NGC4874. The bright, bloated star above them is HD 112887 with an apparent brightness of 7.2mag, which can be spotted with binoculars already. But these two already mentioned galaxies are visually available with 20cm aperture telescopes.

Coma Cluster (Abell 1656) is located about 320 million light-years away from us. It is one of the first places, where observed gravitational anomalies were considered to be indicative of unobserved mass – dark matter. It was in 1933, and currently, the scientists believe, that about 90% of the mass of the Coma Cluster is in the form of dark matter.

Image technical data:

Date: 9-12 May, 2021
Location: Nieborowice, Poland
Telescope: Meade ACF 10" f/10
Corrector: AP CCDT67
Camera: QHY163M
Mount: SW EQ6
Guiding: ASI2190MM + SW ED72
Exposure: 300x2 minutes
Conditions: Bortle 6, transparency good, seeing medium