There is an immense number of galaxies in an immense number of clusters out there. The closest clusters are hundreds of millions of lightyears away, so they are pretty dim, The individual galaxies are typically dimmer than magnitude 15 and beyond, so deep exposures are needed. Anyhow, one can observe several of the closest clusters with modest instruments.
Abell Galaxy Cluster AGC 2151, The Hercules Cluster.
This famous galaxy cluster is part of the Hercules Supercluster, which also is a part of the so called Great Wall Super Structure. AGC 2151 houses some 200 galaxies, where many are spirals. Denoted above are also 2 quasars of magnitude around +18 to 19.
Abell Galaxy Cluster AGC 426, The Perseus Galaxy Cluster.
This famous galaxy cluster could be one of the most massive objects in the universe. It contains several thousand galaxies. It is also said to be the strongest X-ray emitting galaxy cluster in the sky, coming from the region of NGC 1975. This is the brightest galaxy in the centre of this image. The X-ray source is designated Perseus-A, or Perseus-X1, or 3C 84.
Abell Galaxy Cluster AGC 1656, The Coma Galaxy Cluster.
This famous galaxy cluster is one of the major ones. It contains some 1000 galaxies, mostly ellipticals, as well as S0 galaxies, and many anonymous dwarf galaxies. Fritz Zwicky noted very early (1933) that the velocities in the Coma cluster were too high for the galaxy cluster to be bound together by the visible materia of the galaxies. He stated that they must be held together by some "dunkle materie". It is said that some 90% of the materia could be dark matter in this cluster.
www.galaxies.se - Ivar Hamberg - Updated 2020, Sept 01