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(IAAC) Obj: Abell 1656 (Coma galaxy cluster) - Inst: 20" f/5 dobnewt



Observer: Lew Gramer
Your skills: Intermediate
Date and UT of Observation: 1997-03-7/8, 04:30 UT
Location: Westford, MA, USA (43N)
Site classification: semirural
Limiting magnitude: 6.0 (zenith)
Seeing: 4 of 10 - medium good
Moon up: no
Instrument: 20" f/5 truss dobsonian reflector
Magnification: 70x, 210x, 360x
Filters used: None, DeepSky
Object: Abell 1656 (Coma Cluster)
Category: Cluster of Galaxies
Constellation: Com
Data: mag 11 (brtest 11.8)  size 4o(!)
RA/DE: 13h00m  +27o59m
Description:
This was my first look at Abell 1656 - for it's own sake -
in the 20". I had seen ngc4889, ngc4874, and one or two of
the other cluster members on previous occasions, but never
appreciated the real nature of this vast, rich field as a
whole. Although I had too little observing time to do this
monster justice, here is a short report of the brightest few
objects I noted in that first, casual scan of the nearest,
brightest galaxy cluster outside the Local Supercluster!
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A1656 is easily found from faintish blue Beta Com, by star-
hopping first to 41 Com, a wide pair of mags 5 and 6, which
point WNW to a lonely wide trio of stars, mags 7, 8, and 9.
The bright members of the cluster are just SE of the Smost
of this trio of stars, and the whole cluster engulfs them.
-
  ngc 4889	mag 11.8	size 3'x2'	type E4
This unimpressive haze patch was clearly elongated E-W, and
showed what looked like a stellar nucleus. From the outer halo
(about 2' wide) to the center, it brightened fairly evenly and
gradually, right to the "nucleus". No other features seen.
  ngc 4886	mag 13.8	size 1'x1'	type E0
No hint of this little companion to ngc4889 was noted. With more
concentration and use of high power, it should be visible though.
  ngc 4874	mag 11.8	size 2'x2'	type E0
Absolutely featureless haze to my eyes. Some brightening in the
middle to averted vision. The halo was less than 3', faint.
  ngc 4872	mag 14.4	size 2'x2'	type SB0
Even with fixated vision and high power, no sign of this companion
to ngc 4874 was visible. Hazy night? Inattention? You decide!
  ngc 4898a/b	mag 13.5	size <1'	type EP/EP
This twin, faint pair was just detectable as a non-stellar "dot"
to the SW of ngc4889, using fixated averted vision. Somewhat of
a thrill to see these tiny interacting galaxies, but certainly
nothing of their bizarre nature was apparent to my casual eyes.
  ngc 4921	mag 12.2	size 3'x2'	type SB(rs)ab
At the outskirts of the central "field of galaxies", this little
haze-patch can actually just be fit inside a low-power field with
the other two "behemoths", ngc4889 and ngc4874. To averted vision,
it shows a hint of elongation N-S, with little or no mottling to
reveal it's spiral nature. There is a well-defined center, visible
to even direct vision, making it a pretty trio with the other gxs.
  ngc 4911	mag 12.8	size 2'x1'	type SAB(r)bc
Another faint outlier of the inner core of Coma, this galaxy was
actually easy to spot in the field with averted vision, but showed
no detail at 70x. I had no time to apply higher powers or filters
to it, which is unfortunate as I know it can show intriguing detail
for such a faint galaxy, if it's paid sufficient attention!
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That's all! I'll certainly have a longer, more loving look at this
little field of fuzzies if moon & clouds allow later this Spring!