sponsored by psychohistorian.org
RA: 18h 07m 36s
Dec: −23° 20′ 0″
Ch: MSA:1392, U2:339, SA:22
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 21r
Mag: B=8.65, V=8
Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "the middle of a great and rich cluster in the milky way."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 13' and the class as 4 3 r.
The RNGC (Sulentic and Tifft 1973) notes that this is a 8.5 mag open cluster.
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "8M; 13' diameter; large and scattered; 80-plus 11M and dimmer members."
Steve Coe, observing with a 13" f/5.6, notes: "Bright, large, rich, compressed. I counted 55 stars with a very fuzzy backround and many chains of stars at 100X."
Location: Jonkershoek Nature Reserve, Assegaaibosch Station
Date: 1998 July 31 / August 01, 01:00-02:40 SAST
11x80 tripod-mounted binoculars (9.5 mag stars at times not easy)
Sky conditions: Mediocre (transp. low, seeing average, dew) The skies are showing the effects of the combination of pollution (mainly from a nearby wood-processing plant) and a stable inversion layer, turning daytime skies grey-blue, and night skies ashen.
Small cluster near Lagoon & Trifid nebulae. With 9.5 mag stars tonight not effortless, I carefully cross-checked the position of this cluster, and at best can call it a vague smudge bordering on three tiny stars [shown on U339]. Averted vision shows a hazy patch, but very indistinctly -- at times, I think its only the three stars and not much else.
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.