M21 = NGC6531 ( 18h 04.6m -22°30´, 5.9 mag. )
This open cluster in Sagittarius was found by Messier on June 5, 1764. This group of about 60 stars is approximately 4,100 ly away. M21 is visible 30' NE of Trifid Nebula (M20 - see finder chart below).
The above image was taken on July 9, 1999 from Sooke, BC. Cookbook 245 LDC CCD camera was used on unguided Ultima 8 f6.3 telescope. Eight white exposures (60 sec. each) as well as cyan, magenta and yellow-integrations (4 x 60 sec. each) were processed with AIP4WIN software and adjusted in Lab color space using Corel PhotoPaint 8.
North is to the right.
Map created in Guide 7.0 - 7°45' x 12°. North is up.
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© Jan Wisniewski