Galaxy Cluster
Corona Borealis
RA 15:22:50 (approximate center of the group)
DEC +27:43:00
Size:
Magnitude: 15.5 to as faint as you can go…
AGC 2065, the Corona Borealis Galaxy Cluster, is well known for being about 1 billion light years distant and consisting of myriads of closely spaced and faint galaxies. A few of the individual galaxies are magnitude 15.5 or so, but most are fainter so the cluster presents challenges no matter what size scope an observer points here.
Edwin Hubble discovered this cluster in the 1930’s and one of its galaxy members, PGC 54876, was used by Milton Humason in 1936 to help determine the famous distance/velocity relationship that shows the universe is expanding. PGC 54876 is one of the brighter members of AGC 2065, so if you can see any of the individual galaxies in this group, this should one of them.
AGC2065_MegaStar2.jpg
George Abell came along in the 1950’s and included the Corona Borealis Galaxy Cluster in his catalog of Rich Cluster of Galaxies, with AGC 2065 being entry 13.
More recently, AGC 2065 has been shown to be gravitationally bound to several other galaxies clusters that will coalesce into a single group in a few billion years.
I first saw AGC 2065, or at least a few of its members with my old 20 inch f5 scope in the 1990’s, but it wasn’t until last summer that I got around to pointing my 28 inch scope in its direction. Already well down in the west I still got a spectacular view of bunches of faint galaxies:
“Abell 2065 is the very definition of “lumpy darkness”. When I first found the field of view I could see a mottled texture more than individual galaxies, but 408x and determined averted vision showed me the individual galaxies shown in my sketch. But even so, the size and orientation is uncertain because there are so many galaxies here that are so faint. 21.61 SQM” (21.85 the following night).
Abell2065GC crop.jpg Abell2065GC cropInvert2.jpg
The first portion of the cluster to catch my attention was the three galaxies grouped together near the center of the cluster, PGC’s 54880, 54881 and 54883. Being far enough away from the two bright-enough-to-be-irritating field stars helps, as does the tight and distinctive triangle they make. I found this a good place to start my galaxy hops through the rest of the cluster.
There’s something of an unofficial and friendly competition to see who can detect the most galaxies visually in AGC 2065. Regardless of the winning score so far, all I know is that I have a long way to go to catch up!
"GIVE IT A GO AND LET US KNOW"
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