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RA: 18h 01m 50.58s
Dec: −08° 57′ 31.6″
Ch: MSA:1320, U2:294, SA:15
Ref: SIMBAD, SEDS
Type: globular cluster
Mag: B=11.08, V=10.23
An elusive, small globular cluster in Ophiuchus, it is only 4' across and of magnitude 10.3
Synonyms: H II-199
Discovered in 1784 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "pB, pL, R, gbM, r."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "pB, R, gpmbM, 40 arcseconds." On a second occassion he called it "globular, F, R, psbM, 1.5', resolvable, with left eye I discern the stars in it."
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
p.178: "Six clusters noted in Lick Obs. Bull., No.219 (Descriptions of 132 Nebulae and Clusters photographed with the Crossley Reflector) are not included in the catalogue.
NGC 6517: appears as a nebulous star.
(Sulentic and Tifft 1973) notes that this is a 13.0 mag globular cluster.
RA 18 01 50.6 (2000) Dec -08 57 32 Integrated V magnitude 10.23 Central surface brightness, V magnitudes per square arcsecond 17.77 Integrated spectral type F8 Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 1.82 Core radius in arcmin .06. ["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) ]
Only 13th magnitude and 0.5' in diameter, NGC 6517 can easily be mistaken for a field star. Houston has observed it with a 10-inch reflector but has failed to see it in a 4-inch refractor.
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "12M; 1' diameter; bright and round; unresolved; center very compressed, nearly stellar; midway and a bit SE of a line between Tau OPH and Nu OPH."
Steve Coe, using a 13" f/5.6, notes: " Pretty faint, considerably large, brighter in the middle, elongated NE to SW, I cannot resolve this cluster with any power up to 220X. The field of view is very star poor and this dark field may exhibit so much extinction that I am not able to resolve any stars on the face of this globular."
Observer: Steve Coe
Your skills: Advanced (many years)
Date/time of observation: 25 July 98
Location of site: Strawberry, Arizona USA (Lat +34, Elev 7000 ft)
Site classification: Rural
Sky darkness: 8 1-10 Scale (10 best)
Seeing: 7 1-10 Seeing Scale (10 best)
Moon presence: None - moon not in sky
Instrument: 13" f/5.6 Newtonian on Bigfoot German EQ
Magnification: 100X, 220X
Object(s): NGC 6517
Category: Globular cluster.
Data: mag 10.3 size 4'
Position: RA 18:02 DEC -08:58
NGC 6517 The field of view is very star poor and this dark field may exhibit so much extinction that I am not able to resolve any stars on the face of this globular. 100X--pretty bright, pretty small, round, much brighter middle, easy to see as non-stellar. 220X--about all the power this object can take, a little fuzzy at the edges, averted vision makes it grow larger, no resolution. Core is elongated 1.5X1 in PA 45.
1997 July 7, Monday, 21:00 - 24:00 Jonkershoek. 11x80's tripod-mounted. Can see 9.5 mag easily, but the cluster is not visible.
Observing site: Little Tycho Observatory
[18h 1m 48s, -8° 58' 0"] An extremly low contrast brightening of the sky. Invisible in the 25, barely visible in the 12.5.
The Messier objects
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