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RA: 16h 57m 36s
Dec: −44° 49′ 0″
Ch: MSA:1460, U2:407, SA:22
Ref: SIMBAD, DAML02, Archinal&Hynes (2003)
Type: open cluster, 22m
Mag: B=8.72, V=8.2
Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "cluster VIII class, coarse, p rich, stars 9..12th mag." On a second occassion he called it "VII class, p rich, loose irregular figure, large and small stars, 9..15th mag, 10' long, 7' broad."
The NGC records it as "pretty rich, very little compression, irregular outline, stars large and small."
Bailey, examining a Bruce plate (Harvard Annals, Vol 72, No 2), describes it as "Milky Way, coarse cluster of a dozen pretty bright stars, and many faint stars, diameter 10'."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 7' and the class as 2 2 p.
It is detached from the surrounding starfield, and is weakly concentrated towards the centre. There is a moderate range of stellar magnitudes present, although there are only about 30 stars in the cluster.
Vogt. N. & Moffat, AFJ (1973), "Southern Open Star Clusters III." Astron.Astrophys.Suppl., 10, 135-193. [image, table]
d = 1.03 kpc, earliest Sp = B3.
The RNGC (Sulentic and Tifft 1973) notes that this is a 9.5 mag open cluster.
Steve Coe, observing with a 17.5" f/4.5 at 100X, notes: "Pretty bright, pretty small, not compressed, 15 stars at 100X.
A 15.5-inch telescope working at 220 power shows this strange gathering as more like an asterism of 10 stars than an open cluster. It is difficult to see which stars are cluster members and which are field stars. Centering on the cluster's position, one sees four stars forming a False Cross-asterism, to the northwest a tiny parallelogram made up of four stars, and to its northeast 3 stars lying in a curve. Dotted around these are many, much fainter stars.
16-inch f/10 SCT (127x)
Lovely medium cluster with about 15 stars in a horse shoe shape. The open side is more or less to the east. Show a more prominent part to the north and fainter but more dense part to the SE. Nice grouping more or less 6' in size, which is outstanding against the background star field.
The Messier objects
The Bennett objects
The Caldwell list
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