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RA: 03h 14m 42s
Dec: +47° 13′ 48″
Ch: MSA:78, U2:63, SA:4
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003), Skiff20080430-s
Type: open cluster, 22r
Mag: B=9.16, V=8.4
Discovered in 1786 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a beautiful compressed and rich cluster of small and large stars 7' or 8' diameter. The large stars arranged in lines like interwoven letters."
Observations with the 72-inch f/8.8 speculum telescope at Birr Castle noted "Nov 23, 1848. Coarse, cluster strongly honey-combed. Would probably look annular with eccentric eyehole if it were far enough to be a nebula. Nov 21, 1851. The honey-combed appearance is caused by the disposition of the brighter stars; no spiral arrangement."
Trumpler (Lick Obs. Bulletin, Vol 14, No 420) gives the diameter as 7' and the class as 3 2 r.
Photo Index by Jim Lucyk: Sky&Tel. 1/84 p97, Burnhams V3 p1452.
The RNGC (Sulentic and Tifft 1973) notes that this is a 9.0 mag open cluster.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part IV. M.N.R.A.S., 36(2), 58.
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
Tom Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "8.4M; 10' diameter; 150-plus 12M members; 2 brighter stars in foreground; very rich."
Listed by the Herschel Club, described as "large, surface brightness and contrast is low,elusive, some 40 stars with 5 bright stars standing out within grouping, loosely scattered and irregular. 6-inch, 48x."
Houston notes that this cluster can be seen in binoculars, and is set against the Milky Way's rich backdrop. He called it a "sprawling 7th mag cluster that affords a fine binocular sight. In most instruments its diameter will be nearly that of the moon, and about 40 stars will be visible. A white 8th mag star is conspicuous on the edge of this group."
& Cr 38 & Mel 18 & OCL-389; 03 14.7 +47 14
17.5: about 100 stars at 220x in 10' diameter. Rich in mag 13.5-14 stars and includes four mag 12 stars along the W side. Rougly circular outline and uniform but no concentration to the center, many stars are arranged in lanes. A mag 8.5 star is off the S edge and a mag 9 star is about 5' off the ENE edge.
13: about 75 stars in a dense cluster. Includes bright stars on the N side.
Observing site: Little Tycho Observatory
[3h 14m 42s, 47° 15m 0s] Needs averted vision to see the stars. A brightening of the milky way in this light pollution.
The Messier objects
The Bennett objects
The Caldwell list
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