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RA: 18h 09m 15.68s
Dec: −25° 54′ 27.9″
Ch: MSA:1392, U2:339, SA:22
Ref: SIMBAD, Archinal&Hynes (2003), SEDS
Type: globular cluster
Mag: B=9.08, V=8.06
Synonyms: H IV-012
Discovered in 1785 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "F, L, iR, inclining to meridian, 3 or 4' diameter, like a brush to a N.p. star but probably unconnected."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "globular, vF, a little oval, vglbM, barely resolvable, stars 20m, one star 14m, diam in RA = 7.5 seconds."
The NGC describes it as faint and large, slightly elongated, very gradually a little brighter towards the middle, partially resolved, some stars seen, consisting of stars of 20th magnitude.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
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.
Burnham notes that this globular cluster "is one of the most difficult globulars to resolve, as the obscuration in the region appears to exceed 6 magnitudes!"
pF, rather sparse globular cl., 5'x5', showing a curious structure n. of centre, in a very rich field.
The RNGC (Sulentic and Tifft 1973) notes that this is a 10.0 mag globular cluster.
RA 18 09 15.6 (2000) Dec -25 54 28 Integrated V magnitude 8.06 Central surface brightness, V magnitudes per square arcsecond 18.15 Integrated spectral type G4 Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.17 Core radius in arcmin .55. ["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) ]
Hartung notes that "it appears as a rather faint haze just resolvable on occasion with a 12". There is little central condensation and it is markedly elliptical, about 2' by 1.5', in a field sprinkled with stars.
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "10M; 2' diameter; faint, small and elongated; 1.6 degrees SE of M-8; DBL ST ADS 11096 (5" separation; 7.6-13M) in same 0.5 degree field to S."
Steve Coe, observing with a 13" f/5.6, notes: "Bright, pretty large, much compressed, round, about 4 stars resolved at 135X. Averted vision helps. There is an 11th mag star on the NW side."
"Very faint. It contains a star in the nnp border." Gabriel Giust, 1994 April 10, 8-inch f/6.7 reflector, 9.7mm Super Plossl, San Isidro, Buenos Aires.
12-inch Meade, 40mm eyepiece, 53' fov. 1997-08-05, fair sky conditions "Eliptical globular cluster, just a patch hazy light of medium size with fringed edges. I could not make out any stars or lanes, just a faint star towards the edges of this globular cluster." [Magda Streicher, Pietersburg 23-53S, 29-28E]
12-inch f/10 SCT (EP: 2-inch 40mm SW 76x 53' fov; 2-inch 14mm UW 218x 23' fov)
Elliptical in shape in a north to south direction. Just a hazy glow. With averted vision and high power (218x) the core get slightly brighter. The fringes delicate and sandy, but I could still not resolve any stars. A white 9.5 magnitude star can be seen 5' arc minutes to the east.
Location: Jonkershoek Nature Reserve, Assegaaibosch Station
Date: 1998 July 31 / August 01, 01:00-02:40 SAST
11x80 tripod-mounted binoculars (9.5 mag stars at times not easy)
Sky conditions: Mediocre (transp. low, seeing average, dew) The skies are showing the effects of the combination of pollution (mainly from a nearby wood-processing plant) and a stable inversion layer, turning daytime skies grey-blue, and night skies ashen.
Very, very faint bloated star, not much brighter to the middle. Not easy tonight; needs averted vision and attention.
23 August 1993, 00:25 Observing with 11x80's from Stellenbosch, NGC 6553 was not seen whereas the nearby NGC 6544 could be picked up.
1994-06-04 23:00, Die Boord, 11x80. Good seeing. Smaller than nearby NGC 6544, this cluster can be seen with the same care it takes to see NGC 6544. Quite a nice grouping of stars in the immediate surrounds of this small patch of soft light.
1997 April 21. Jonkershoek. 11x80 tripod-mounted. No moon. Smaller version of NGC 6544; a nucleus-less small patch.
Location: Vineyards outside Stellenbosch
A short distance away [from NGC 6544] is NGC 6553, a moderately bright object, round, pretty evenly illuminated and not noticeably brighter to the middle. A small star (V=11.1) is embedded in its north-western extreme. It appears to be about twice the size of its neighbour, NGC 6544. Two 10th mag stars to the south-east have the same separation as the globular's diameter (about 2.5 arcminutes).
Observing site: Little Bennett Regional Park
[18h 9m 18s, -25° 54' 0"] Faint, large, but barely resolved. In the southern soup, it would be much better south of the equator!
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's stars are unresolved and that this cluster has a round hazy mist of light.The central core of this cluster is very faint and that there is some condensation in the nucleus of this cluster.This globular cluster measures 4.3'*4.3'Chart:No.320,NSOG Vol.2.
The Messier objects
The Bennett objects
The Caldwell list
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