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RA: 17h 46m 18s
Dec: +05° 43′ 0″
Con: Ophiuchus
Ch: MSA:1273, U2:203, SA:15
Ref: SIMBAD, DAML02, Archinal&Hynes (2003)
Type: open cluster, 32m
Mag: B=4.49, V=4.2
Size: 70′
PA: ?
IC 4665. See IC 4651.
"cluster; coarse; diameter 30'; 10 stars, 7-10th magnitude."
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.
Mel 179: A few bright stars forming a very open cluster. Not in NGC but noted by Bailey.
"A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.
Mel 179 : "a few bright stars." He gives the approx. diameter as 60 arcmin.
(Lick Obs Bul, Vol 14, No. 420) gives the diameter as 50' and the class as 2 2 p.
Harrington notes that this cluster, although not as rich as other clusters, "stands out surprisingly well thanks to its spartan surroundings. Your finderscope or binoculars will show about 10 stars there, while a 6- to 8-inch telescope increases this number threefold ... high magnifications will ferret out a trio of double stars near the middle of the group."
Lorenzin, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "6M; 1 degree diameter! very large and sparse; 20-plus 7M members; visible with the naked eye; great binocular object."
Date and UT of Observation: 1997-07-25/26, 05:15 UT; Location: Medford, MA, USA (42N); Site classification: urban; Limiting magnitude: 5.8 (zenith), intermittent haze; Seeing: 5 (out of 10 highest) - mediocre; Moon up: yes, 50% (not visible at site); Object: ic4665
7x50 binoculars; A pretty grouping of 10 stars, mags 7 to 10, which formed a tiny "Grus-like" or lambda shaped asterism, pointing due N. IC4665 was VERY easily found, just NE of the E "shoulder star" (beta) of Oph. An intriguing and - I suspect - oft overlooked binocular target!
Coe, using a 13" f/5.6, notes: " is a very large open cluster that is scattered over at least one degree of sky. It barely fits in the 18" with a 2" Giant Erfle eyepiece. Even so, the cluster aspect is lost and there are just 40 pretty bright stars in the field. My best view of this cluster is with an 8" f/4.5 at 25X. The brighter cluster members are obvious and there are about 100 dimmer members. The field contains many nice chains of stars and several wide double stars. From a dark Arizona site the cluster is naked eye and my 10 X 50 binoculars provide a nice view."
1995-06-01: 11x80. Kelsey Farm. 22:00 SAST. Beta Ophlies to its south-west. A Very neat little cluster, lying in a rich filed. It is scattered, difficult to get its full extent. The orange-yellow Beta lies to the south-west. I see here a loop of nine stars with a little tail of three stars leading off to the northwest, just like the capital letter Q. And then smack in the middle of this loop sits another little star. A neat little grouping. Pronounced. Reminds me somewhat of the Beehive.
1997 July 7, Monday, 21:00 - 24:00 Jonkershoek. 11x80's tripod-mounted. Wonderful! Naked eye object, which shows a roundish fuzzy globular-like glow. Binoculars show a scattered cluster, distinctly spread out but still forming a whole. Look for the Q of about 20 stars. Neat!
Observing site: Little Tycho Observatory
Telescope: C-8
[17h 46m 18s, 5° 43m 0s] A large cluster of around 20 bright (6-8mv) stars. This would be best in binoculars, seen from a dark sky site.
Lacaille's catalogue
The Messier objects
Dunlop's catalogue
The Bennett objects
The Caldwell list
Named DSOs
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