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RA: 17h 02m 40.4s
Dec: −39° 44′ 18″
Ch: MSA:1460, U2:407, SA:22
Ref: SIMBAD, DAML02, Archinal&Hynes (2003)
Type: open cluster, 22p
Mag: B=?, V=9.5
James Dunlop discovered this object from Paramatta, New South Wales, and included it as No. 521 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "2 rows or lines of pretty bright small stars in the parallel of the equator, with a multitude of minute stars resembling a faint nebula, 5' diameter."
Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "cluster, rich, pL, brilliant, 8', stars irregularly scattered 10..12th mag, place of a double star in the following angle of a triangular condensed group." On a second occassion he called it "a p rich irregular cluster of nearly = stars 10th mag, not mbM, 7'."
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 7' and the class as 2 2 p.
The RNGC (Sulentic and Tifft 1973) notes that this is a 9.5 mag open cluster.
Photo Index by Jim Lucyk: Vehrenberg's Atlas of DS Splendors (3ed) p171.
Steve Coe, observing with a 17.5" f/4.5 at 100X, notes: "Pretty bright, pretty small, somewhat rich, irregular in shape at 100X. This cluster is a long star chain with a few other members forming branches to the chain.
10x50 tripod-mounted. 1997-07-06. "small blury blob, very faint" [Rui Henriques]
1995 May 24, 21:00 Jonkershoek. 11x80. Quite easily seen as a small glow with maybe two stars included.
In a two-inch refractor this cluster is very interesting; although small and faint, it looks like a dull glow. Careful examination with averting to the wide pair of stars to the east, shows a striking long chain of stars through the centre, running north-east south-west. It appars like a broken line of equally bright stars, the number indeterminate. There are three star chains; the central one (mentioned above) is flanked by two more: the western one only has three members, and is of the same length. The chain to the east is much shorter. A truly strange cluster because no other stars excepting the chain member can be seen! In all, a poor oc, with one large prominent chain of equally bright stars flanked by 2 lesser chains.
In a 15.5inch telescope it is shown as a poor cluster which is elongated west-east. In fact, it appears to be nothing more than 2 loose chains of stars, side by side. The northern chain terminates in a triangle of stars, and the southern chain has a pair of star, of which the southern most one is slightly red. The majority of stars are of a similar magnitude with a few considerably fainter ones also present.
The Messier objects
The Bennett objects
The Caldwell list
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