Astrophotography by Anthony Ayiomamitis

Deep Sky Object Image Gallery

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: Open cluster NGC 6811 in Cygnus depicted below is a cluster comprised of approximately 70 member stars which are of uniform brightness and very well detached from the background sky. The cluster spans 15 arc-minutes in diameter or half the apparent diameter of the full moon. Depending on the source, the cluster lies between 2940 and 3960 light-years away (heliocentric distance) with an intermediate age of approximately 700 million years old and as evidenced by the presence of some red giants and predominance of white hot stars in the image below. The small galaxy to the bottom right of the image below is PGC 2277519 (mag 16.7, 0.6'x0.3'). The cluster is best observed using low magnifications (50-100x) during summer when it is directly overhead and can be found to lie just to the northeast of -Cyg (mag 2.90). NGC 6811 was discovered by John Herschel in 1829.

Please click on the image below to display in higher resolution (1200 x 950)

Image Details
NGC 6811 - Open Cluster in Cygnus
Imaging Details
NGC Number:
6811

Common Name(s):
Hole in a Cluster

Other Designations:
Cr 402, OCL 185

Object Type:
Open Cluster

Object Classif:
III 1 r

Constellation:
Cygnus

RA / Dec:
19h 37m 18s /
46 23' 20"


Distance:
2940-3960 ly

Object Size:
15' x 15'

Magnitude:
6.8
Date:
July 11, 2010
00:10 - 2:25 UT+3


Location:
Athens, Greece

Equipment:
AP 160 f/7.5 StarFire EDF
AP 1200GTO GEM
SBIG ST-10XME
SBIG CFW10
SBIG LRGB + IR-block


Integrations:
Lum :  030 min (10 x 3 min)
Red :  030 min (05 x 6 min)
Green :  030 min (05 x 6 min)
Blue :  030 min (05 x 6 min)
Binning :  1x1 (Lum),  1x1 (RGB)

Image Scale:
1.16" per pixel

Temperatures:
Ambient : + 19.0 C
CCD Chip : - 12.5 C

Software:
CCDSoft V5.00.195
CCDStack V1.6.0.5
eXcalibrator V1.0.3.0
Aladin V6
Photoshop CS2