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RA: 18h 55m 6.2s
Dec: −22° 42′ 2.8″
Ch: MSA:1390, U2:340, SA:22
Ref: SIMBAD, Collinder (1931), NGC/IC, SEDS
Type: globular cluster
Mag: B=11.29, V=10.35
NGC 6717. IC 4802 (which see) is a clump of stars in this globular.
Synonyms: H III-143
Discovered in 1784 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "3 vS stars with suspected nebulosity."
Observed by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "Close, to the south of, v2 Sagittarii; a very small clustering knot, with perhaps nebula. A doubtful object. I see 3 or 4 of the stars, but there is also a nebulous appearance."
Catalogued as Palomar 9.
See Abell G O "Globular Clusters and Planetary Nebulae discovered on the National Geographic Society - Palomar Observatory Sky Survey" (1955) PASP Vol 67 No 397 p258. In this article, the diameter is listed as 2.6', the brightest stars are 16.5 magnitude and the concentration rating is 8.
RA 18 55 06.2 (2000) Dec -22 42 03 Integrated V magnitude 9.28 Central surface brightness, V magnitudes per square arcsecond 16.48 Integrated spectral type F6 Central concentration, c = log(r_total/r_core); a 'c' denotes a core-collapsed cluster 2.07c: Core radius in arcmin .08. ["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) ]
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 3' and the class as 2 2 p.
William P. Clarke (San Diego, California, USA) writes in the The Webb Society Nebulae and Clusters Section Report No. 10, July 1992: "Not resolved. Round, with 2 stars or bright spots on N.E. edge and another one on the W edge, and also a bright knot at the centre. Looks almost like a face-on spiral galaxy. (21-inch f/20, x140, x350)."
The RNGC (Sulentic and Tifft 1973) notes that this is a globular cluster.
This globular cluster can be seen with a 13-inch and 17.5-inch reflector, notes Steve Gottlieb.
Barbara Wilson's Globular Cluster Observations
NGC/IC: 6717 OTHER: Palomar 9 OBJECT_TYPE: Globular
CONSTELLATION: Sagittarius SIZE: 3.9'LISTED_MAGNITUDE: 8.35
RA/DEC: 1855.1-2242 DATE: 9-18-93 TIME: 11:20 PM SITE: COLUMBUS, TEXAS
SEEING: 6 TRANSPARENCY: 6.5 TELESCOPE/INSTRUMENT: 20" F/4
EYEPIECE(S): 7mm MAGNIFICATION(S): 285 FILTER_TYPE: no EYEPIECE_DRAWING:
no SOURCE: Brian Skiff
V(TIP): 13.0 V(HB): 15.73 CLASS: 8
DESCRIPTION_AND_NOTES: Class 8 globular, and brightest of the Palomars. semi resolved, small round glow with 5 stars seen within the glow. Double star seen to northeast wide pair to the south and star near center. Brightest stars are 13 mag, horizontal branch mag is 15.73. Reobserved on 8/14/93 10:30 PM In the glow of 35V Sag (mag 5.8) this glob has bright stellar center and 3 stars superimposed with a bright circular glow around the 3 stars. 35 V is a yellowish star with a tinge of orange. The 3 stars form a triangle near the center of the globular they are 10-12th mag. Modern Discoverer: Abell Actual Discoverer: William Herschel Distance: 6.6 kpc.
Steve Coe, observing with a 13" f/5.6, notes: "Pretty faint, small, round, grainy at 165X. Going to 285X will not resolve with globular, but it does show three stars very near to the cluster, two on the east and one on the west side."
The Messier objects
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