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RA: 17h 00m 42s
Dec: −44° 40′ 0″
Ch: MSA:1460, U2:407, SA:22
Ref: SIMBAD, Collinder (1931), DAML02, Archinal&Hynes (2003)
Type: open cluster, 22r
Mag: B=8.85, V=8
James Dunlop discovered this object from Paramatta, New South Wales, and included it as No. 456 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "a very large patch of strong nebula, about 20' long, and 16' broad, rich in small and extremely minute stars."
Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "a superb, vL, v rich cluster, which fills field; R, vglbM, stars 11..12th mag, thickly sown at intervals from each other from 10 to 20 arcseconds." On a second occassion he called it "vL, v rich, fills more than a field, has one or two straggling appendages p and s; stars 11 and 12th mag, nearly equal."
The NGC records it as "Remarkable! Cluster, bright, very large, very rich, stars from magnitude 11 and fainter."
"cluster, fairly condensed."
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
"Cat. of Open Cl. south of -45° Decl.", Mem. 17 Mnt Stromlo Obs.
Raab, S. (1922) A research on open clusters. Lund Medd. Astron. Obs. Ser. II, 28, 1.
Discussed, based of F-A plates.
Bailey, examining a Bruce plate (Harvard Annals, Vol 72, No 2), describes it as "Milky Way, coarse cluster of several hundred faint stars, diameter 20'."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 16' and the class as 4 2 r.
The RNGC (Sulentic and Tifft 1973) notes that this is a 8.5 mag open cluster.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Steve Coe, observing with a 17.5" f/4.5 at 100X, notes: "Bright, large, very rich, round, reminds me of NGC 7789 in Cassiopeia at 100X. This cluster is cut into pieces by dark lanes.
In a 15.5-inch reflector the cluster consists of pretty faint stars and appears well spread out with the stars evenly distributed. It is not very well detached from the moderate starfield.
The Messier objects
The Bennett objects
The Caldwell list
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