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NGC 6558
NGC 6558, Cl Collinder 368, C 1807-317, Cl VDBH 259, ESO 456-62, GCl 89, h 3731, GC 4382
RA: 18h 10m 18.38s
Dec: −31° 45′ 48.6″
Con: Sagittarius
Ch: MSA:1415, U2:377, SA:22
Ref: SIMBAD, Collinder (1931), SEDS
Type: globular cluster
Mag: B=12.39, V=11.29
Size: 4.2′
PA: ?
Historical observations
John Herschel (1847) Cape Observations
Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "globular, pB, irreg R, gmbM, composed of stars 16m, on a milky way ground of mixed L and vS stars." On a second occassion he called it "globular, pB, R, gbM, 80 arcseconds, resolvable or resolved in a field very full of milky way stars." His third observation was recorded as "globular, not vB, R, glbM, 2', resolved. The stars barely discernible."
Published comments
Hinks, A.R. (1911)
Hinks, A. R. (1911) On the galactic distribution of gaseous nebulae and of star clusters. MNRAS, 71(8), 693-701.
List 6: "NGC numbers of clusters classed as globular, not in Bailey's catalogue"
Bailey, S.I. A catalogue of bright clusters and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Harris, W.E. (1997)
RA 18 10 18.4 (2000) Dec -31 45 49 Integrated V magnitude 9.26 Central surface brightness, V magnitudes per square arcsecond 17.08 Integrated spectral type F7- Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 2.50c: Core radius in arcmin .03. ["Catalog Of Parameters For Milky Way Globular Clusters", compiled by William E. Harris, McMaster University. (Revised: May 15, 1997; from http://www.physics.mcmaster.ca/Globular.html; Harris, W.E. 1996, AJ, 112, 1487) ]
Sulentic & Tifft (1973)
The RNGC (Sulentic and Tifft 1973) notes that this is a globular cluster.
Helwan Obs. Bulletin No 21 (1920)
vS cl. about 1'x1'; probably should be classed as globular.
Helwan Obs. Bulletin No 22 (1921)
Confirms HOB 21.
Melotte, P.J. (1915)
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Modern observations
Steve Coe
Steve Coe, observing with a 13" f/5.6, notes: "Pretty bright, pretty small, round and has a very bright middle. I could resolve 10 members at 220X."
Contemporary observations
Auke Slotegraaf
1993 April 30
30/04/93: I searched in vain for this cluster with the 6-inch f/8.6 Newtonian at 52x and 72x.
Tom Bryant
2008-07-03 00:00:00
Observing site: Pinnacles overlook
Telescope: C-8
[18h 10m 18s, -31° 46' 0"] A small, very faint cluster, not granulated. It was not easy at 163x, and was almost invisible at 36x
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Favourite lists
Lacaille's catalogue
The Messier objects
Dunlop's catalogue
The Bennett objects
The Caldwell list
Named DSOs
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