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RA: 23h 08m 26.68s
Dec: −15° 36′ 41.3″
Ch: MSA:1353, U2:303, SA:17
Ref: SIMBAD, Archinal&Hynes (2003), SEDS
Type: globular cluster
Mag: B=?, V=11.2
Synonyms: H III-558
Discovered in 1786 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "eF, cL, iR, 5' or 6' diameter."
Described in the NGC as "extremely faint, large, between two double stars."
The RNGC (Sulentic and Tifft 1973) notes that this is a 12.5 mag globular cluster.
RA 23 08 26.7 (2000) Dec -15 36 41 Integrated V magnitude 11.29 Central surface brightness, V magnitudes per square arcsecond 21.33 Integrated spectral type - Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.00 Core radius in arcmin .83. ["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.
Hartung notes that "this is a very uncondensed cluster since the apparent diameter is 3.5' and, as the integrated magnitude is only 12.3, it is a very faint telescopic object. However, 20cm will show it and with 30cm it is a large round patch of faint fairly even haze showing evidence of very faint stars. This is a good test for a clear dark night; as a guide it lies between a faint star and a faint wide pair 7' following; about halfway somewhat south."
In my opinion, the toughest NGC-globular would be NGC6749 in Aquila. It has also wrong coordinates in many sources, has a low surface brightness and is in a rich star field. NGC7492 in Aquarius, NGC6426 in Ophiuchus and NGC1049 in the Fornax Dwarf are other NGC-toughies.
0.2 deg SE of NGC6380, there is a dark nebula called SL28. Has anybody seen it?
Timo Karhula "Amateur astronomers are * *
E-mail: firstname.lastname@example.org nocturnal creatures" * * *
ICBM: +59d52'13" +16d05'22"
----------------------------------------------------------- * *
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "12.5M; 3' diameter; a real TOUGH cookie! straddled on either side by 13.5M stars; wait for dark skies and culmination; not much center brightness for a GLOB."
Steve Coe, using a 17.5" f/4.5, notes: "Extremely faint, pretty small, round, not much brighter in the middle at 100X. This is a very low surface brightness globular with no stellar resolution at any power. If you are ready to take an observing break, this an easy object to locate. Put Delta AQR in the field of a low power eyepiece, turn off the drive and take a 13.7 minute break. When you return to the scope NGC 7492 will be in the field, honest. It was very faint, pretty small, round and not much even at 165X. It was not easy in the 17.5" on a night I rated 8/10 for transparency."
Cuffey: * off E side: V=13.1; brtr * NW: V=12.9; * S: V=14.5; * SSW: V=14.2.
15cm - fairly f losfbr glow 4' diam @ 80x. m13 * off E side, m12.7 * NW, m14 * SSW. almost due S close to edge is m14.5 *, like this (sketch in notes). 140x shows def gran/mottling, but no obvious *s except at threshold. wk broad concen. cl easy to spot @ 50x. BS, 14Oct1990, Anderson Mesa.
25cm - not vis, though fld was centered using Lick Atlas. BS, Roof.
30cm - vf, vpoorly condensed; best at hix. sev threshold *s in vuneven concen, dk in center giving impression of ring-like shape. found 15' E of two dbl*s. CBL, Roof.
1997 October 28, Tue/Wed: Jonkershoek, seeing 3, transparency 3, sky darkness 4, lim.mag. at south pole 6.0 (naked eye), 10.7 (binoculars). 11x80 tripod-mounted. "Not seen."
1997 November 29/30, Sat/Sun: Jonkershoek, seeing 3, transparency 3, sky darkness 4, lim.mag. at south pole 6.0 (naked eye), 10.7 (binoculars at pole) Strong SE wind. "Careful examination, not found."
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