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RA: 20h 23m 8s
Dec: +40° 46′ 30″
Ch: MSA:1128, U2:84, SA:9
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 13mn
Mag: B=7.13, V=7.4
A member of the Cygnus OB 9 Association.
Synonyms: H VIII-056
Discovered in 1786 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a small cluster of coarsely scattered stars of various sizes, E like a forming one."
In the 5th edition of Webb's Celestial Objects for Common Telescopes it is described as "beautiful group .. half degree north of gamma, little following."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 13' and the class as 4 3 p.
Vorontsov-Velyaminov, B. (1925) "Catalogue of integrated magnitudes of star clusters", Astron. Nach. 226.195. Comparing the brightness of the cluster with the extrafocal images of stars, he estimates the magnitude as 6.68.
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.
The RNGC (Sulentic and Tifft 1973) notes that this is a 7.5 mag open cluster.
Photo Index by Jim Lucyk: Observer's Guide (Astro Cards) 9-10/87 p24.
MacRobert notes that in his 6-inch at 50x "the group is obvious the moment it's swept up. The brighter stars are arranged in straight lines that look for all the world like a stick-figure horse in profile pulling against a rope - perhaps a rocking horse, with the two bright orange stars for feet. Its facing northwest; certainly a unique little pattern. Continued use of averted vision with the 6-inch brings glimpses of many additional fainter stars swarming through the group ... under darker skies a 6-inch scope might show the fainter cluster members much better."
8x40mm - circle of *s around gamma Cyg; cl is a sl patch in the Nrn arc. BS,
7cm - sm cl of f *s strewn btwn two m6-7 *s. 75x: 15 *s besides two br ones,
irreg concen. pair lies S of NWrn br *, is first * vis S of this *. BS,
27Nov1992, Anderson Mesa.
15cm - 10' diam w/25 or so *s. HM/BS, 27Jun1970, FtL.
- about 1/2-deg N of gamma Cyg. two br *s at each end. the fntr *s run in
btwn in an oblong shape. about 12 *s vis w/in 5' area. HM/BS, 1Jul1970,
- looks sparse @ 80x, not well sep from fld. two m7 *s at each end NE &
SE. 140x: much more interesting. 35 *s in 5' diam, most of brtr *s
strung btwn the two m7 *s. NWrn br * has two f comps on E; m9 * S of
this * has two f comps on opposite sides (~E&W); f pair SW of this. SE
of this btwn the two m7 *s is another un= pair. knot of rel f *s
surrounds SErn m7 *. BS, 17June1991, Anderson Mesa.
20cm - mod br cl. 25 *s vis @ 125x in 5' area, m10+.
25cm - fairly br. end *s m7.5. 20 *s in 5' circle. br *s elong btwn end *s,
elong SE-NW. on N are f ones to be incl among cl members. *s on S are
30cm - 149x: 25 *s bwtn br pair. loose.
The Messier objects
The Bennett objects
The Caldwell list
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