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RA: 18h 12m 42s
Dec: −21° 36′ 0″
Ch: MSA:1392, U2:339, SA:22
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 41m
Mag: B=?, V=8.6
Synonyms: H VII-030
Discovered in 1786 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a cluster of pS scattered stars, above 15' diameter."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "cluster VIII, loose, scattered, fills field, is decidedly richer than any part of the milky way that has occurded to-night."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 15' and the class as 3 1 m.
The RNGC (Sulentic and Tifft 1973) notes that this is a 8.5 mag open cluster.
Journal BAA, 36, Nov, p58
L coarse cluster of irr.form.
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "8.5M; 13' diameter; 50-plus members; large, scattered group 35' SSW of 4M Mu SGR; 10' to the ESE is 5.5M 14 SGR and TL-3, the "HSL Chain"."
Steve Coe, observing with a 13" f/5.6, notes: "Pretty bright, large, pretty rich, somewhat compressed, 33 stars within 10 arcmin at 100X, a nice globular of pretty faint stars."
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.
With 9.5 mag stars at times difficult, this cluster wasn't noticed while sweeping. Determined its position with care, and it still did not yield.
The Messier objects
The Bennett objects
The Caldwell list
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