Abell Galaxy Clusters
Observable in an amateur telescope
by Steve Coe

George Abell died several years ago but one of the most enduring legacies he has left astronomy is a catalog of galaxy groups that he compiled in the 1950's. Abell surveyed the then recently completed Palomar Sky Survey plates to find clusters of galaxies. He assigned numbers according to richness of the number of galaxies and the distance of the cluster. He found that the magnitude of the 10th
brightest galaxy was a good indicator of the relative brightness of the cluster. This ground breaking work has stood the test of time as a valuable system for evaluating galaxy clusters.

This file contains information on the 29 Abell galaxy groups that got assigned distance values of "0" or "1". Brian Skiff has observed many of these clusters over the years and he informed me that this is a very resonable criteria for making a list of the best and brightest galaxy clusters. Seeing as how the information I have received from Brian has been excellent in the past, that is the criteria I chose for this listing.

The magnitude column is for the 10th brightest galaxy in that group. The Uranometria chart number column will contain several chart numbers if the area of the sky overlaps more than one chart. The size listing is in either arc minutes or square degrees depending on which type of information I could find.

My observations of a few of these galaxy clusters are included. There is also a photo reference if a picture of this cluster has been in Sky and Telescope, Deep Sky or Astronomy magazine. If the cluster is covered in the Observer's Handbook by Luginbuhl and Skiff (L&S) then there is a reference to a page number.

Some of the objects in these clusters are going to be a test for a large amateur telescope even on the best of evenings.

Abell 262: There are two centers to this galaxy cluster. One is around NGC 708, it is pretty faint and round at 135X in my 13". There are three other galaxies around NGC 708, all very faint, one is round, two are elongated. The other center of Abell 262 is NGC 785, it is pretty faint, round and brighter in the middle. It is surrounded by four fainter galaxies.

Abell 347: Using the 13" f/5.6 in the Arizona desert on a night I rated 8 out of 10 for seeing and transparency, I could see 2 faint members and 6 other very faint members. This not a rich group and several pretty bright stars are involved within the group.

Abell 426: NGC 1275 is the central galaxy in the Perseus I cluster of galaxies. It is pretty faint, small and little elongated at 165X in my old 17.5" f/4.5 on a night I rated 8/10 for seeing and transparency near Sedona, Arizona at about 5000 feet elevation. With averted vision I could pick out 6 other galaxies within one degree of NGC 1275. This is a pretty rich Milky Way field and that makes deciding what is a galaxy and what is a star quite difficult at times. I have only reported the objects I could definitely identify as galaxies.

Abell 779: In the central mountains of Arizona, the 13" could show me NGC 2832 as a pretty bright, pretty large and round galaxy which is much brighter in the middle at 100X. On an excellent night using 165X and 220X, I could also see nine companions around NGC 2832. In moments of good seeing many extremely faint members make the field mottled or "lumpy".

Abell 1060, The Hydra Galaxy Cluster I on a night near Kitt Peak that I rated 8/10 for seeing and 9/10 for transparency, all observations done at 165X in a 13" f/5.6.

Abell 1367: I have observed this group on several occasions, I will report on two that will demonstrate that on these type of difficult objects, aperture makes a big difference in what can be observed. The first observation is using the 13" in the desert at 165X and 220X. The central, pretty faint, galaxy is quite easily detected and it has four other galaxies within one half degree. Five other very faint galaxies will show themselves if I use a dark cloth to cover my head and block out stray light, even 100 miles from Phoenix in dark skies. From the same site, using Pierre Schwaar's 20" f/5 at 180X, I counted 22 galaxies, I know that none can be classified as "easy", but they could be pointed out to friends, when they were at the eyepiece. Also, the big mirror showed some detail within the galaxies that could not be seen at any power in the 13". As we used to say when I was drag racing, "there's no substitute for cubic inches".

Abell 1656: A spectacular region that is "lumpy" from the overwhelming backround of galaxies. NGC 4889 and 4874 are the center of this rich cluster. Both are pretty bright, pretty small and roundish. NGC 4889 has a bright core that makes it stand out brighter than any other cluster members. It is also surrounded by a swarm of very small, very faint galaxies. The cluster is one degree in size. Dr. Fritz Zwicky surveyed this cluster and identified 804 galaxies brighter than 16.5 magnitude, so don't worry about running out of goodies to observe. This group of distant galaxies is best observed from the darkest of sites on the best of nights. I use a dark cloth to cover my head and block off stray light. This is a tough field to draw accuratly, the red flashlight on the paper makes the dimmest members disappear. Using the dark hood I can see a total of 5 pretty faint members and 20 very faint members on a night I rated 9/10 for seeing and transparency. That is using the 13" f/5.6 at 165X and 220X on a superior evening at 7000 ft. in the mountains of central Arizona. There is an excellant picture of this cluster in Sky and Telescope,
May 1980 on page 366, it is what I used to find my way in this cluster.

Abell 2065: Using Pierre's 20" at 180X, we could see 2 members that were classified as very faint and another 4 galaxies that we only suspected. In moments of good seeing, the field of view was mottled from galaxies just as the limit of detection.