|Right Ascension||17 : 46.3 (h:m)
|Declination||+05 : 43 (deg:m)
|Visual Brightness||4.2 (mag)
|Apparent Dimension||70 (arc min)|
Discovered by De Cheseaux 1745-6.
IC 4665 is a very conspicuous, coarse star cluster in the opera glas, but difficult to detect in the telescope so that neither Messier nor one of the Herschels found it. The Sky Catalogue 2000.0 gives 30 member stars, the brightest of which is of 6.86 magnitude, a Trumpler type of III 2 p, and an estimated age of 36 million years. At a distance of 1,400 light years, IC 4665 is approaching us at 12 km/sec.
IC 4665 has been discovered by the Swiss astronomer Philippe Loys de Cheseaux, according to the Webb Society Deep-Sky Observer's Handbook, Volume 3 (Open and Globular Star Clusters), p. 3.
The image in this page was obtained by Till Credner and Sven Kohle of the University of Bonn, Germany when evaluating their Constellation Ophiuchus photography. The photo was obtained on May 2, 2000 at 03:45 UT with f=50mm f/4.0 lens on Kodak Royal 400 Select color print film from Tenerife, Spain. It was exposed 35 min; the original image has a 27x39 deg field of view; our image is a magnification of a small region from this field, around IC 4665. The bright star in the lower right (SW) of IC 4665 is Beta Ophiuchi, a red giant of spectral type K2 III and apparent visual magnitude 2.77 (not associated with the cluster).
In John Caldwell's Best Sky Objects list. In the Astronomical League's Deep Sky Binocular Club List.
Last Modification: 4 Oct 2000, 14:00 MET