The Coma Galaxy Cluster, Abell Galaxy Cluster (AGC) 1656, contains more than 800 galaxies brighter than photographic magnitude 16.5. It’s a real galactic forest that will take great patience to make your way through.  There is no rushing this one.  Unless you have enough time to devote to the task, best to push on to another target and come back here when you do.  In fact, you will never get through this huge collection of galaxies in one sitting.  Or even two, three, or four sessions, for that matter.  AGC 1656 could well take years before every galaxy in view is recorded and identified.

Where, oh where, to begin?  Making our way through the cluster may take time, but finding it does not.  The geometric center of AGC 1656 lies 2¾° west of Beta (β) Comae, the star at the right angle of the constellation's triangular outline.  The cluster covers the 3¾° gap between 31 Comae at its western edge and 41 Comae just inside its eastern border, and is centered very near 7th-magnitude SAO 82595.

The table at the end of this article lists 74 of the cluster's galaxies that are brighter than 15th magnitude.  That's your assignment, to see as many as you can.  There simply is not enough room to describe them all here, but here are a few highlights to kick off your project.

We will begin with NGC 4874 and NGC 4889 at the heart of the cluster, both depicted in  the digitized sketch below.  Both are bright enough to be within the range of 8-inch instruments, although glare from SAO 82595 may hamper their visibility.  NGC 4889, the more obvious of the two, is a giant elliptical galaxy in the spirit of the monster galaxy M87 in the Virgo cluster.  But while M87 is some 60 million light years away, NGC 4889 is projected to be 308 million light years distant. Taking that into account, NGC 4889 is actually the more luminous of the two.  As with M87, astronomers have detected strong emissions emanating from the core, the signature of a supermassive black hole. Through the largest backyard telescopes, NGC 4889 displays a fairly bright, oval disk elongated east-to-west and surrounding a brighter core.

Although it is a little smaller and fainter than its neighbor, elliptical galaxy NGC 4874 is no slouch.  You'll find it just 7' west of NGC 4889 and 6' due south of SAO 82595.  Again, we find a strong radio source buried deep within the core of the galaxy.  Visually, NGC 4874 strikes me as more than 0.1 magnitudes fainter than NGC 4889, despite the listing.  Look for a round glow that draws to a brighter central core.

The best view of both galaxies comes at 200x or more, since the resulting narrow field helps to move that distracting star out of view.  Once the glare is gone, suddenly, a swarm of smaller, fainter companions begin to dot the field.  With averted vision, I can count no fewer than 9 island universes.  NGC 4886 is superimposed over the northwestern edge of NGC 4889; NGC 4883 about 4' to the northwest of its core; NGC 4894 just 2' east-southeast of the core, and NGC 4898 a little further to the southeast still.  On dark nights, PGC 44763 and PGC 44771 pose even greater challenges.  Look for the PGC pair 5' east of NGC 4889.  Beyond them, lie IC 4042, IC 4041, and IC 4040, along with NGC 4906.

That covers the eastern half of that single eyepiece field; NGC 4874 and its brood still lie in the western half.  Two galaxies drift nearby.  Can you spot NGC 4872, which appears superimposed on, or perhaps immersed in, the larger galaxy's southwestern edge?  NGC 4871 is also close at hand, just 1' west of the galaxy's core.  Finally, watching these two smaller companions is NGC 4873.  Look for it just 1.5' to the northwest.  All three shine between 13th and 15th magnitude and are smaller than 1 arc-minute across.

You might be able to spot a lone island universe floating a third of the way from NGC 4874 back toward NGC 4889.  That's IC 3998.  This extremely faint, round system forms a close pair with PGC 44652 just 1' to its south-southeast.  Several other members of the PGC listing also hover near NGC 4874, including PGC 44636 and PGC 44656 to its north. None of these marginal objects has a surface brightness greater than perhaps half a magnitude above background, so you may need to boost magnification even further to maximize image contrast.

Expanding the view some, look for the interacting pair of NGC 4864 and NGC 4867 about 5' west of NGC 4874.  At 200x, I can only make out a very dim, distended blur, but increasing to 300x helps resolve the individual cores, which are separated by only 35".

From NGC 4889, scan slowly toward the southwest to find NGCs 4853 and 4854, a pair of tiny 13th-magnitude spirals separated from one another by 5' and lying just to the north of an 8.5-magnitude field star.  Slide 17' due west of that star to find the elliptical galaxy NGC 4839 and another horde of fainter companions.  NGC 4839 shines at about 12th magnitude and is the brightest galaxy in this quadrant of the cluster.  Through my 18-inch (46cm) reflector at 206x with averted vision, it appears as a soft, oval glow tilted southwest-northeast around a brighter core.  Photographs expose a small companion superimposed just to the southwest of the core, but I have never been able to resolve it individually.  Averted vision may, however, reveal several smaller, fainter galactic smudges in the same field, including the double system NGC 4842A/4842B just 2½' to the southeast. NGC 4840 is also in the picture, 7' north-northeast of NGC 4839.

Selected Members of AGC 1656 Brighter than Magnitude 15

(Highlighted entries are discussed above)

This brief summary is not even the tip of the galactic iceberg that awaits the largest backyard telescopes here.  Hundreds of faint fuzzies can be found within the 4° span of AGC 1656.  But to hunt them down, you will need several detailed charts that show the area at a sufficiently large enough scale and plot field stars faint enough to wade your way through this intergalactic maze.  Use the chart here to identify as many as you can, but as mentioned previously, to go deep into a galactic ocean like AGC 1656, you need customized charts for your specific telescope and eyepieces.

For more information and observing tips on observing AGC 1656 and other Abell Galaxy Clusters, visit Alvin Huey's website, faintfuzzies.com. There, you will find information about his online book Observing Selected Small Galaxy Groups as well as other volumes in his deep-sky observing guide series.

Have a favorite challenge object of your own?  I'd love to hear about it, as well as how you did with this month's test.  Contact me through my website or post to this month's discussion forum.

Until next month, remember that half of the fun is the thrill of the chase.  Game on!