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RA: 06h 20m 48s
Dec: −07° 17′ 0″
Ch: MSA:275, U2:272, SA:11
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 22m
Mag: B=8.85, V=8.45
Synonyms: H VII-020
Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a beautiful cluster of pretty compressed and equally scattered stars, 10' or 12' diameter."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 8.5' and the class as 2 2 p.
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
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 8.5 mag open cluster.
Listed by the Herschel Club, described as "circular in shape, faint stars with a brighter star seen to one end, 10 stars counted, tightly grouped. 6-inch, 48x."
Ken Reeves, in "SACNEWS On-line for March 1997", observing with a 10-inch f/4.5 scope, notes: "NGC 2215 (06 21.0 -07 17) At 70x, I saw this cluster as pretty big, somewhat bright, not very rich or condensed. There were 2 levels of stars with a star count of about 25 stars. The cluster is triangular or arrow head in shape pointing to the E."
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "9M; 8' diameter; large and rich; 25-plus 11M and dimmer members; midway and S of a line between Beta MON and Gamma MON."
Location: ASH Naylor Observatory, Lewisberry, PA
Conditions: Seeing - fair, Transparency - good, Limiting magnitude - 5.0
Instrument: 17" f/15 classical Cassegrain
Ocular: 2" 32mm Konig-II (202x)
This compact Herschel 400 open cluster lies between the excellent triple star Beta Monocerotis and Gamma Monocerotis. It has a somewhat diamond-like shape and consists of 10 or more stars varying in brightness.
Steve Coe, observing with a 13" f/5.6, notes: "is bright, large, pretty rich, round and compressed at 165X. I counted 42 stars, some in nice chains. Seen in the 10X50 binoculars."
Steve Coe (Glendale, Arizona, USA) observing with a 13.1-inch f/5.6 reflector, writes in The Webb Society Nebulae and Clusters Section Report No. 11, January 1993: "Forty-two stars counted in this bright, large, round and compressed cluster. Some stars in nice chains at x165. Also seen in 10x50 binoculars."
Observing site: Little Tycho Observatory
[6h 21m 0s, -7° 17' 0"] A scattering of around 10 8-10.5mv stars with about 25 fainter ones misting around them.
The Messier objects
The Bennett objects
The Caldwell list
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