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RA: 18h 08m 2.2s
Dec: −43° 42′ 19.7″
Con: Corona Australis
Ch: MSA:1457, U2:409, SA:22
Ref: SIMBAD, Archinal&Hynes (2003), SEDS
Type: globular cluster
Mag: B=8.06, V=7.32
discovered this object from Paramatta, New South Wales, and included it as No. 473 in his catalogue of 1827. Using a 9-inch f/12 telescope, he described it as "a very bright round highly condensed nebula, about 3' diameter. I can resolve a considerable portion round the margin, but the compression is so great near the centre, that it would require a very high power, as well as light, to separate the stars; the stars are rather dusky."
Observed 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, e comp, v Fine; diameter of most comp part = 11 seconds of time in RA; stars 15..16m. The scattered stars extend to three times the diameter and die away very gradually." On a second occassion he called it "B, R, gbM, diam in RA = 6 seconds, easily resolvable. The left eye resolves it (Query semi-diameter.)"
Bailey, examining a Bruce plate (Harvard Annals, Vol 72, No 2), describes it as "remarkable globular cluster, bright, pretty compressed, several hundred faint stars, diameter 12'."
"! globular cluster, 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 8.0 mag globular cluster.
RA 18 08 02.2 (2000) Dec -43 42 20 Integrated V magnitude 6.30 Central surface brightness, V magnitudes per square arcsecond 15.58 Integrated spectral type F6- Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 2.00c: Core radius in arcmin .30. ["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.
Notes: "The combination of this globular cluster and its starry field is most beautiful; it is well condensed, round and resolved into gleaming stars, the outliers up to 6' across. 15cm shows stars in it but it is only mottled with 10.5cm and is an easy luminous haze with 7.5cm."
Harrington, P. (1986) An observer's guide to globular clusters. Sky&Telescope, Aug, 198. this lcuster is another victim of poor location … one of the brightest .. measures 13' across and even from my home on Long Island I have viewed some of its 13th mag stars with an 8inch refelctor and moderate power.
Cozens calls this an impressive cluster, noting that it lies in a rich Milky Way field which "adds luster to the view."
Alcaino: * E prob m~11.0 (also on AA).
6x30mm finder - vis w/sub*ar nuc.
6cm - well concen clear to nuc w/prominent * on E side. 2'.5 diam. pretty br. Slate Mtn.
13cm - 60x: br, mod broad concen. m11.5 * lies on E edge. 5Jun1983, USNO.
25cm - vbr, 3' diam w/sharply rising core. partially res (less than 5deg above horizon). outliers spread thin quickly and seems more extensive to W. dk patch follows. Slate Mtn.
- at meridian, 190x. 5' diam, much better res than obs #1 indicates. BS, 9Jul19080, Anderson Mesa.
30cm - 125x: partially res w/doz of *s. broad core 1' diam, outliers to 3'. just off S edge of core is sm grp of *s making core therefore appear virreg in outline. pretty well res @ 250x. outliers spread thinly to 5' diam. 5Jun1983, USNO.
Observing from Stellenbosch, 1983, I saw this cluster in a 2-inch refractor at 20x as marked conveniently by a bright star. It is faint and small, and appears like a slightly defocused bright star. One could easily sweep right over it if one does not look very carefully. Best seen with averted vision.
1997 October 27: Jonkershoek, seeing 3, transparency 3, sky darkness 4, lim.mag. at south pole 6.0 (naked eye), 10.7 (binoculars). 11x80 tripod-mounted. "Easy; round fuzzy ball in the field with several very bright stars."
1997 April 21. Jonkershoek. 11x80 tripod-mounted. No moon. Bright, round, glow, neat contrast to the bright star north-west.
12-inch Meade, 40mm eyepiece, 53' fov. 1997-08-05, fair sky conditions "A medium sized globular cluster, just about to reveal small faint stars towards the fringes, which run towards the far outside of the field. Compressed and brighter towards the middle, with an uneven disk. Dark lanes become visible but you have to look very carefully." [Magda Streicher, Pietersburg 23-53S, 29-28E]
16-inch f/10 SCT (127x, 290x)
This globular look like a spiders cocoon nest. Wide dense core which looks slightly hazy.
12-inch f/10 SCT (EP: 2-inch 40mm SW 76x 53' fov; 2-inch 14mm UW 218x 23' fov)
A packed round globular cluster, with a very condensed wide bright core. The outskirts reveals pin-point stars spraying away into the field of view. Dark lanes become visible around the edges between the short star outliers, and needs careful observation (218x). A faint 11th magnitude star can be seen near the eastern edge and another 8th magnitude star 13' arc minutes to the west of the globular. Averted vision, do justice to this globular cluster.
Observing site: Pinnacles overlook
[18h 8m 0s, -43° 42' 0"] A miniature M 13.
Location:Night Sky Caravan Park, Bonnievale.
Sky Conditions:Whole Milky Way is visible.The sky is clean.
Atmosphere stable with little interference.
The stars in this globular cluster looks like a bright snowball where the stars are clearly resolved in this cluster into a multitude of bright stars.Around the outskirts of this cluster there is plenty of bright stars being resolved.The nucleus of this globular cluster is centrally concentrated and that the nucleus is brighter compared to the stars on the far outskirts of this cluster.This globular cluster measures 5.6'*5.6'.Chart:No.107,NSOG Vol.2.
The Messier objects
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