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RA: 18h 03m 50.69s
Dec: −00° 17′ 48.9″
Ch: MSA:1296, U2:249, SA:15
Ref: SIMBAD, Archinal&Hynes (2003), SEDS
Type: globular cluster
Mag: B=?, V=9.3
An elusive globular in Serpens Cauda that was missed by the two Herschels, and wasn't discovered until 1852 when the English asteroid hunter J.R. Hind chanced upon it.
Small loose cluster of a few bright stars. No nebulosity
Included in a list of doubtful objects;. A small cluster, on the edge of a rich region, with few stars.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
The RNGC (Sulentic and Tifft 1973) notes that this is a 12.0 mag globular cluster.
RA 18 03 50.7 (2000) Dec -00 17 49 Integrated V magnitude 10.47 Central surface brightness, V magnitudes per square arcsecond 20.22 Integrated spectral type G0- Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.30 Core radius in arcmin .42. ["Catalog Of Parameters For Milky Way Globular Clusters", compiled by William E. Harris, McMaster University. (Revised: May 15, 1997; from http://www.physics.mcmaster.ca/Globular.html; Harris, W.E. 1996, AJ, 112, 1487) ]
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "11M; 1.5' diameter; unresolved, small glow with bright core; three 13.5M stars superimposed in a line just W of core."
Houston calls it a challenge for any observer. It is only 1' across and magnitude 12. He failed to find it with a 4-inch refractor, but a 10-inch showed it with little difficulty. Yet, adds Houston, Sagot and Texereau in Revue des Constellations notes that this cluster is visible in 2- and 3-inch low-power telescopes. Houtson calls it inconspicuous: "Of the 11th magnitude and only 1.3' in diameter, it requires a careful search. Once located, it should be inspected with a magnification of 100 or higher."
Hartung, observing with a 12-inch, calls this a small faint object, resolved into a few stars on a hazy irregularly round area about 1' wide. With a 6-inch, only a dim roundish haze with a very faint star or two is seen.
Steve Coe, observing with a 13" f/5.6, notes: "Pretty bright, pretty large, round, much brighter in the middle. The 17.5" scope resolves 5 stars at 165X."
Observing site: Little Bennett Regional Park
[18h 3m 48s, -0° 18' 0"] A rather faint blob, but there was a hint of resolution in it. Very loose, class X? Burnham: class XI.
The Messier objects
The Bennett objects
The Caldwell list
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