Galaxy Cluster, Abell 566
The galaxy cluster Abell 566 is located no less than 1.3 billion light-years away from us in the constellation Camelopardalis. Using the redshift
of z=0.098, the escape velocity is calculated as v= 28,000km/s, which corresponds to around 9% of the speed of light.
The inner area of the cluster is around 4' in size, which corresponds to a true diameter of 1.5 million light-years. There are around 50 galaxies in
this area, so the cluster has a relatively high density of galaxies. The brightest galaxy has a magnitude of 17.4 bmag and an apparent size of 0.8x0.4',
which corresponds to a diameter of almost 300,000 light-years. It is therefore a cD galaxy (central dominant).
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Even in my 20" f/3 Dobsonian, the observation is not easy. This is because the galaxies are all very faint and usually have a brightness of less
than 17mag. So you not only need a dark sky, but also good seeing.
Nevertheless, almost 20 galaxies were visible at a magnification of 380x, most of which are located near the center. You can also see the
densification towards the center very well in the telescope. The galaxy cluster reminds me a little of Abell 2065 in CrB, even if the latter is a
little easier to observe.
In any case, it is amazing that you can still observe a galaxy cluster 1.3 billion light-years away with a 20" aperture under a dark sky. That
alone is worth the effort. :)
