sponsored by psychohistorian.org
RA: 17h 27m 44.33s
Dec: −05° 04′ 35.9″
Ch: MSA:1322, U2:248, SA:15
Ref: SIMBAD, SEDS
Type: globular cluster
Mag: B=?, V=9.5
The RNGC (Sulentic and Tifft 1973) notes that this is a 12.0 mag globular cluster.
Photo Index by Jim Lucyk: Vehrenberg's Atlas of DS Splendors (3ed) p181.
RA 17 27 44.3 (2000) Dec -05 04 36 Integrated V magnitude 9.20 Central surface brightness, V magnitudes per square arcsecond 21.24 Integrated spectral type - Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster .92 Core radius in arcmin 1.83. ["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) ]
A loose cluster of vF stars some 15'x15'
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
This globular cluster lies a quarter of a degree east of 47 Ophiuchi, and Walter Scott Houston reports that it appears only 3' across in his 4" refractor, and about 5' across in the 20" Clark refractor at Van Vleck Observatory, Connecticut. The globular's concentration rating is 11/12, and Houston notes that in the 20-inch "it appears more like a highly compressed open cluster."
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "12M; 4' diameter; fairly large, faint and unresolved with little brighter center; 11 and 12M stars to NW; 12 and 13M stars superimposed a few seconds N of core; 10' due E of 5M 47 OPH."
Steve Coe, using a 13" f/5.6, notes: " Faint, large, round, not brighter in the middle at 135X. I counted 11 stars when I raised the power to 220X on this low surface brightness globular. It is somewhat strange for a globular in that it is not compressed at all. It looks like a pretty faint open cluster with several brighter members. When a friend looked into the eyepiece, he said it looked like oatmeal. I agreed."
1995-06-01: 11x80. Kelsey Farm. 22:00 SAST. East of 47 Oph. This globular looks very much like an internal reflection of the reasonably bright 47 Oph near. Needs averted vision to show it clearly as a vague hazy image.
1997 July 7, Monday, 21:00 - 24:00 Jonkershoek. 11x80's tripod-mounted. Very faint cluster, with 47 Oph due west. A small star precedes the cluster, between cluster and star. Requires attention and a star chart to locate. Not casually seen. One of the faintest clusters Ive yet seen.
Observing site: Pinnacles overlook
[17h 27m 42s, -5° 5' 0"] A faint, diffuse object at the southern end of a 4 star chain. Hard to see.
The Messier objects
The Bennett objects
The Caldwell list
DOCdb is still in beta-release.
Known issues, feature requests, and updates on bug fixes, are here:
Found a bug? Have a comment or suggestion to improve DOCdb? Please let us know!
DOCdb is a free online resource that exists to promote deep sky observing.
You could help by sharing your observations, writing an article, digitizing and proof-reading historical material, and more.
Everything on DOCdb.net is © 2004-2010 by Auke Slotegraaf, unless stated otherwise or if you can prove you have divine permission to use it. Before using material published here, please consult the Creative Commons Attribution-Non-Commercial-Share Alike 2.5 License. Some material on DOCdb is copyright the individual authors. If in doubt, don't reproduce. And that goes for having children, too. Please note that the recommended browser for DOCdb is Firefox 3.x. You may also get good results with K-Meleon. Good luck if you're using IE. A successful experience with other browsers, including Opera and Safari, may vary.