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RA: 18h 18m 37.65s
Dec: −52° 12′ 54.6″
Ch: MSA:1494, U2:434, SA:26
Ref: SIMBAD, SEDS
Type: globular cluster
Mag: B=10.32, V=9.56
Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "globular, B, R, gmbM, entirely resolved into stars 16m; easily seen." On a second occassion he called it "globular, pB, R, gpmbM, 2.5' or 3' diam, easily resolved with left eye into stars 15m."
Described in Union Obs. Circulars, 45-76, p 50. "Nebulae, clusters, etc. on Sydney Plates" as "a fine little cluster, about 4' in diameter."
"globular cluster, fairly condensed"
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
The RNGC (Sulentic and Tifft 1973) notes that this is a 9.5 mag globular cluster.
RA 18 18 37.7 (2000) Dec -52 12 54 Integrated V magnitude 8.27 Central surface brightness, V magnitudes per square arcsecond 17.79 Integrated spectral type F6 Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.20 Core radius in arcmin .59. ["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) ]
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Gerd Bahr-Vollrath (Noosa Heads, Queensland, Australia) observing with an 8-inch f/12 SCT, writes in the The Webb Society Nebulae and Clusters Section Report No. 10, July 1992: "Fairly small and faint glow. A brighter irregular mottled core is surrounded by a faint, round envelope. Appears grainy throughout."
ASV Journal Vol 24 No 3 June 1971: "easy, but not resolved in 4-inch."
1997 Sept 03: 11x80 tripod-mounted. 23:00 SAST. Jonkershoek. Reasonably easy, round nebulous glow, easily pinpointed as one corner of a triangle with two stars north.
1998-04-23/24, 11x80 tripod-mounted binoculars, Die Boord. Seeing good, transparency below average, dew. "South of two 8th mag stars is this delicate round glow, confirmed with averted vision, which shows it might be up to 4' across. Not much else can be seen in the 11x80's, except that the light does not grow brighter to the middle."
12-inch Meade, 40mm eyepiece, 53' fov. 1997-08-05, fair sky conditions "Another faint globular cluster,a little brighter towards the middle with mollted edges. Towards the nothern side three stars form an arch around the globular cluster. No pin-point stars, although stars are seen to become visible." [Magda Streicher, Pietersburg 23-53S, 29-28E]
12-inch f/10 SCT (EP: 2-inch 32mm SW 95x 42' fov; 2-inch 14mm UW 218x 23' fov)
Another faint globular cluster, tightly packed towards the middle with slightly mottled edges. Brightens slowly to the core with a tapered down appearance to the south. Towards the northern side three stars form an arch sweeping outwards. No stars are revealed but splinters of light just become visible with averted vision. Faint stars can be seen on the eastern and western periphery.
12-inch f/10 SCT (76x, 218x, 346x)
A lovely round bright haze quite outstanding against the star field. With higher power it shows very faint stars resolved and getting more hazier towards a unresolved core which seems to somewhat out of shape, not round. Three 10.5 magnitude stars embedded into the soft outer western portion was seen immediately. Very busy star field with two much brighter stars to the north.
Location:Night Sky Caravan Park, Bonnievale.
Sky Conditions:Whole Milky Way is visible.The sky is clean.
Atmosphere stable with little interference.
This globular cluster has the shape of a roundish bright snowball where the stars in this cluster are well resolved into bright individual stars.Around the outskirts of this cluster there are chains of bright stars being clearly resolved into hundreds of stars.The central nucleus of this globular cluster is arranged into a tight periphery of stars.The nucleus of this cluster is somewhat brighter than the far outskirts of this globular cluster.This globular cluster measures 9.4'*9.4'.Chart:No.332,NSOG Vol.3.+
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