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RA: 22h 15m 6s
Dec: +49° 54′ 0″
Ch: MSA:1103, U2:87, SA:9
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 22m
Mag: B=6.54, V=6.4
Synonyms: H VIII-075
Discovered in 1788 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a cluster of coarsely scattered large stars, lE sp-nf, 16' long."
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part II. M.N.R.A.S., 35(8), 280.
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 7.41.
The RNGC (Sulentic and Tifft 1973) notes that this is a 6.5 mag open cluster.
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 21' and the class as 3 2 p.
Photo Index by Jim Lucyk: Deep Sky #1 Wi82 p18.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
According to Sagot and Texereau, the cluster appears triangular in a 3.8-inch refractor at 45x. . the number of stars increases from 15 in a 2-inch to 60 in an 8-inch.
Hartung notes: "In a fine field this irregularly scattered cluster of moderatly bright stars without much concentration and about 20' across is fairly effective with small apertures."
Houston, observing with a 12-inch reflector could see no definite shape, but noted at least 80 stars within the cluster. He advises to look for a wide double star at the centre of the cluster, adding that it should be visible in a 6-inch or larger. He calls it a 7th mag cluster about 20' in diameter which is distinct against the star-studded Milky Way.
Listed by the Herschel Club, described as "50 stars counted in thsi loose and rather scattered grouping of stars. 8-inch, 48x."
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "8M; 20' diameter; 40-plus members includes DBL ST Struve 2890 (10" separation; both 8.5M)."
WDS: pair = ADS15785: 9.3,9.5; 9".3; 11.
POSS: blank area (1990 15cm obs) is on due N side.
15cm - 20' diam. many br *s. four sections. curls from E to S then N, like backwards C. 40 *s. HM, Roof.
- lg widespread cl w/little concen that only just stands out @ 50 from excellent Milky Way fld. roughly triangular 15' on-a-side: one apex points E, where a clump of *s is; at SW apex is rel wide m9 pair. nr center is rel close (15") m9.5-10 pair. cannot trace outliers beyond 20' diam---essentially the circle circumscribing the triangle. 80 or 90 *s at 80x to threshold (m~14). rel blank area on NE base of triangle. BS, 14Sep1990, Anderson Mesa.
25cm - 90x: not distinctive from Milky Way. elong NE-SW, 20'x15'. grouped into two lobes w/dk lane btwn. each lobe 7' across w/30 *s. SW lobe contains nice pair, m9.5.
- parabola of *s opening N, incl nice pair (10,10.3; 10"; pa350, bluish) on E side of circlet. 25 *s in or inv w/circlet. E and N are another 40 *s, a little fntr. total diam 30'. BS, 30Aug1981, Anderson Mesa.
30cm - spills out of 22' fld, 25'x18' in pa60. irreg grpings incl one nice pair nr the center w/sl different colors, 10" sep. 80 *s counted, incl bkgrnd. NE part smlr, SW lgr.
The Messier objects
The Bennett objects
The Caldwell list
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