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RA: 20h 03m 55s
Dec: +44° 09′ 30″
Ch: MSA:1128, U2:84, SA:9
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 22r
Mag: B=8.04, V=7.6
Synonyms: H VII-059
Discovered in 1790 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a very rich cluster of large stars, considerably compressed, above 15' diameter, by the size of the stars it is situated in the milky-way, towards us."
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "Fine cluster."
(Lick Obs Bul, Vol 14, No. 420) gives the diameter as 10' and the class as 1 2 p.
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 9.0 mag open cluster.
Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part I. M.N.R.A.S., 35(5), 159.
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
"A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.
"roughly circular; in rich region." He gives the approx. diameter as 15 arcmin.
Photo Index by Jim Lucyk: Burnhams V2 p797, Observer's Guide (Astro Cards) 9-10/87 p11.
Houston calls this "an interesting little cluster . . having several score stars loosely packed in an oval 8' long. Their combined light is about 9th mag. In a 10-inch at 150x, the field of view is filled with sparkling starry excitement."
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "8M; 8' diameter; 50-plus 10M and dimmer members; main body is diamond shaped with tail coming out of the E and arcing S; don't let go that string!."
6cm - 10 *s w/much br haze. elong SE-NW.
8cm - less well res than -11. consp string of three or four *s runs SE-NW
across it. brtst of string is on NW plus a half doz others. a little
hazy. BS, 13Aug1983, Anderson Mesa.
15cm - sm fairly dim cl of 20 *s and unres haze. 5' diam. *s m10+. HM/BS,
- rel poor cl of m11+ *s. core 7'x5', elong SSE-NNW, has 25 *s. brtst on
N has two f comps. outliers difficult to define: seem to spread to
15'x8'-10' elong E-W, with another 40 *s or so. detached grps also N&S,
but these seem less obviously part of the cl. BS, 8Aug1988, Anderson
25cm - 180x: cl elong SE-NW w/many br *s. 8' diam. wide pair SE, un= pair on N
side of center. in 20' fld is lentic series of clusterings elong E-W.
40 *s, m10-11.
30cm - nice cl. sev sm grps in loosely concen cl of 45 *s. brtst part is on W,
elong SE-NW. most outliers extend E & NE, giving overall pa60. arc of
brtr *s runs SE-NW in W part of cl. sev grpings trail to E. 7'x4'
This magnitude 5.6 open cluster in Cygnus shows a nebulous glow in a 6-inch, probably due to unresolved stars. The glow was also apparent with a 10-inch reflector.
The Messier objects
The Bennett objects
The Caldwell list
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