Open star clusters are widely distributed in our galaxy and represent a loose collection of stars which number from a few dozen to a few
hundred stars and are weakly-held gravitationally. Perhaps the three most famous such open clusters are the Pleiades (M45) in Taurus, the
Beehive (M44) in Cancer and the double cluster in Perseus. They are all characterized with a handful of hot and white prominent stars and
nebular material surrounding these stars.
Note: The open cluster NGC 6883 in Cygnus depicted below is comprised of approximately 30 member stars which are not very well detached from the background sky owing to the fact the cluster is in a very rich section of Cygnus and which happens to be also embedded within the eastern end of the nebulosity associated with LBN 182. As indicated by the image below, the cluster is dominated by a handful of bright stars (mag 7-9) including a tight double at its core (mag 9.41 and 9.73) as well as a bright pair of bright red giants to the west (HD 191783, mag 9.25, B-V=3.31 and SAO 69548, mag 8.92, B-V=2.43). The cluster is generally widely dispersed and easily lost in the deep background sky. NGC 6883 spans 15 to 35 arc-minutes in diameter (depending on the source) and is estimated to be 14-16 million years-old while a distance is not available in the academic literature. The small reflection nebula left of center is rather obscure and is simply known as GN 20.10.7. The cluster is best observed using low magnifications (50-100x) during summer when it is directly overhead and a few degrees west of Sadr. NGC 6883 was discovered by John William Herschel (1792-1871) in 1828.
Please click on the image below to display in higher resolution (1200 x 950)
Cr 415, OCL 152
IV 2 m n
RA / Dec:
20h 11m 00s /
35° 51' 12"
35' x 35'
July 12-13, 2010
23:45 - 01:55 UT+3
AP 160 f/7.5 StarFire EDF
AP 1200GTO GEM
SBIG LRGB + IR-block
1.16" per pixel