These observing comments are based upon more than a decade's observing with my 17.5 " f/4.5 Dobsonian, usually at 220X (9mm Nagler). It's fun to scan bright galaxy clusters with wide field, low power eyepieces like the 20mm Nagler, but I find that higher power darkens the sky, increases contrast and makes it much easier to pick up faint cluster members. The best published source for information on observing galaxy clusters, particularly the brighter, better-known ones, is still Volume 5 of the Webb Society Deep Sky Observer's Handbook series.--Jim Shields
Move about 20 ' SSE of Hickson 5 (NGC 190) to find the brightest member of this loose cluster, IC 1565. With a good finder chart you may be able to pick up three more IC galaxies in the same medium power field, all in the mid-15th magnitude range. The cluster is around 600 million light years away.
The brightest member of this cluster, 14th-magnitude UGC 579, lies about 50 arcminutes E of a mag 5 star. UGC 583 is another two arcminutes E and UGC 587 an additional eight arcminutes E. Two fainter cluster members were also located. About 700 million light years away.
This cluster is very rich visually because it is relatively nearby (about 300 million light years). It includes nine NGC galaxies brighter than 15th magnitude within half a degree. The brightest members, at 13th magnitude, are an interesting double galaxy, NGC 545/547 (Arp 308), and NGC 541 (Arp 133). Deep photography shows a faint luminous bridge connecting these galaxies, in which is imbedded a famous peculiar galaxy known as Minkowski's Object. (Picture above)
Identified two cluster members, one of them double. The brightest at mag 13.8 is double galaxy MCG+1-8-27 which appeared elongated NS but not cleanly split. Another much fainter MCG galaxy was located three arcminutes SSW. The cluster is nearly 700 million light years away.
At magnitude 14.6, the brightest galaxy in AGC 407 is UGC 2489, a triple system that appears misshapen and lumpy at 286X, as if composed of multiple cores. There are two other UGC galaxies of comparable brightness in the same field: UGC 2491 six arcminutes S and UGC 2494 16 arcminutes N. The latter is one of those cute edge-ons that looks like it's hanging from a star like an icycle. It turns out that neither of these galaxies is a true member of the Abell cluster, however. They belong to the NGC 1167 group, only about one third as far away as AGC 407. (NGC 1167 itself lies 32' S of UGC 2489.) Around 700 million light years away. (Picture above)
This cluster is centered around UGC 3274 (VV161), a 14th-magnitude galaxy chain about 2.5 degrees west of Bellatrix. An impressive sight in a 17.5" scope, the chain extends NS with 3 or 4 bright knots visible. Also identified were two other 15th-magnitude cluster members, one about 8 arcminutes NNE, the other around 5 arcminutes W. The cluster is fairly close at only 300 million light years. (Picture above)
This galaxy cluster contains four IC galaxies within about 5 arcminutes. (They are misidentified on both Megastar and TheSky.) At mag 14.3, the brightest is IC2376. I picked up the three brightest cluster members with averted vision. Around 750 million light years away.
Abell 779 lies 45 arcminutes SSW of 3rd magnitude Alpha Lynx. Its brightest member is 12th magnitude NGC 2832, with a pair of faint companions. The cluster is relatively far away at 700 million light years and most of its members are fainter than 14th magnitude.
This cluster is a cinch to find, lying about five degrees SE of Regulus and two degrees NW of 4th-magnitude Rho Leonis. It includes three IC galaxies within about five arcminutes, the brightest of which is IC 613 at magnitude 14.8. The cluster is around 500 million light years away.
This cluster is fairly scattered and lies about 500 million light years away. The brightest members, at around mag 14, are NGC3492 and IC664. I found these easily, and thought I glimpsed a couple of other IC galaxies in the cluster.
This is a rich cluster visually, containing six NGC galaxies within a 20arcminute field. The brightest is NGC 3550 at mag 14.1. The second brightest, NGC 3561 (Arp 105), is a peculiar galaxy with a small elliptical known as "Ambartsumian's Knot" attached to the end of a gas plume (not observed). The cluster is about 500 million light years away.
There are actually two galaxy clusters superimposed on the sky here, according to the NASA Extragalactic Database (NED). AGC1213 is around 700 million light years away, while AGC1213A is much closer at 400 million light years. A pair of nearby 10th-magnitude stars make galaxy identification pretty easy in this cluster. The brightest member is UGC6292 at mag 14.4 but the area about five arcminutes south from UGC6292 appeared very clumpy and may be the central concentration. At times I thought I glimpsed a couple of 15th magnitude MCG galaxies there. It was easier to spot the two brightest galaxies in AGC1213A just to the north.
The most prominent feature of this cluster is a line of small faint (15th magnitude) IC galaxies spread across a 12 arcminute field. About 500 million light years away.
Identified four IC galaxies in this cluster, the brightest of which is IC 708 at mag 14. The second brightest, IC 712, lies 8 arcminutes ENE near an 8th-magnitude star. All four appear small and round. About 500 million light years away.
This cluster is also known as Ursa Major I. It's a tough one to observe because of the glare from 5th magnitude SAO28142 just south. (It's easy to find, though.) Hard to believe that this cluster is almost one billion light years away! I had been skunked on this cluster before but I finally managed to pick up the brightest galaxy and a fainter member fortuitously placed near an obvious asterism. The central concentration, however, appeared to lie about 7-8 ' northeast of SAO28142, where there is a very jumbled clumpy area of faint stars and likely intermingled near-stellar galaxies. The lack of bright stars or asterisms made galaxy identification difficult here but I thought I glimpsed the second brightest member of the cluster here. I'd like to see this one in a 30-inch scope! (Picture above)
About two degrees SSW of the Hercules Cluster (AGC 2151), Abell 2147 is at about the same redshift (550 million light years) and is probably part of the same supercluster. Most of its members are faint, small and scattered. The most interesting feature is a short chain of three 14th magnitude MCG galaxies just NW of a 9th magnitude star.
This cluster is dominated by three giant 13th magnitude ellipticals: NGC 6146, NGC 6160 and the cD galaxy NGC 6173. Most of its other members are faint, small and scattered. About 450 million light years away.
This is the archetypical cD cluster. It is dominated by the giant 12th magnitude elliptical NGC 6166, surrounded by many small faint companions. Observing with Steve Gottlieb, we were able to identify five. About 450 million light years away.
Nice compact cluster of three 15th-magnitude galaxies including NGC 6331: ab easy; c (beside star) suspected with averted vision. About 5 arcminutes W of distinctive asterism. This is a very distant cluster: about 900 million light-years away. (Picture above)
This cluster includes three NGC galaxies, two of which appear double on POSS. The brightest is NGC 7018 at mag 14.5, about 8 ' NE of an 8th-magnitude star. It appears elongated EW with separation into two bright cores suspected with averted vision. NGC 7016 and NGC 7017, slightly fainter, lie close together about 3 ' SW. A faint MCG galaxy was also detected. The cluster is about 600 million light years away. (Picture above)
Pegasus I Cluster
This is a fairly loose scattered nearby cluster, about 200 million light years away. Its brightest members are 11th magnitude ellipticals: NGC 7619 and NGC 7626. I found these two and five other NGC galaxies within a one degree field.
Compact cluster around 15th-magnitude NGC 7649, fairly large and diffuse, lying 8 ' S of a 7th-magnitude star. Identified three other cluster members, including a tiny MCG galaxy 5 arcminutes ESE that lies between two 14th-magnitude stars and two anonymous galaxies. IC 1487, shown NE of NGC 7649 by both Megastar and TheSky, is actually a duplicate sighting of NGC 4697 itself, according to Harold Corwin. About 650 million light years away.
This is a very rich cluster, also known as Klemola 44, and it's easy to find, too. The three brightest members--all IC galaxies--lie within a 5 ' circle just 15 ' W of 5th-magnitude Delta Sculptoris. IC 5358, the brightest at mag 13.4, is a double galaxy with PGC 72437. It appears elongated EW and the split is suspected with averted vision. Observing with Steve Gottlieb, we managed to identify 11 cluster members in all: 5 IC galaxies and 6 PGCs. About 400 million light years away. (Picture above)
This cluster features four NGC galaxies within a 5 arcminute field. By far the brightest, at 12th magnitude, is NGC 7768. I also spotted three faint MCG galaxies just to the north.