Abell 21 - Galaxy Cluster
The galaxy cluster "Abell 21" is located in a distance of 1.25 billion light years in the constellation Andromeda near the prominent Pegasus Quadrangle.
If you look at a SDSS image, you can see a giant ellipse in the center with a brightness of 14.1mag. Like many galaxies of this distance class it has an easy to
remember designation: 2MASX J00203715+2839334. ;) If you convert the apparent diameter of 0.66x0.39', the galaxy has a quite impressive size of 240,000 lightyears.
It also appears that the galaxy is undergoing a merger process with another elliptical galaxy.
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And what is visible in the eyepiece? With an aperture of 20" at least a little bit. The large ellipse was not very difficult to see. A small diffuse patch of light.
The other galaxies are a bit more difficult, so a black cloth was quite helpful to get some positive sightings at magnifications close to 300x. If you put all seen
galaxies into a drawing, you get a very nice impression of this very unknown galaxy cluster.
