M21 - Open Cluster

  
 
 
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  • RA: 18:04.6
  • Dec: -22:30
  • Magnitude: 6.5
  • Distance: 4,250 ly
  • Size:  13.0 arc min
  • Constellation:  Sagittarius
  • Scope: 8" SCT at f/10
  • Autoguider:  ST-4 in faint mode
  • Sky conditions:  quite good transparency and seeing
  • Film: Kodak Supra 400
  • Exposure:  20 minutes
  • Date:  August 27, 2003
  
 
Comments:  This turned out to be a much better night than expected with quite good conditions.  The low was in the upper 50s.  I took this shot to buy some time while the telescope equilibrated and chased it almost to the horizon.  The cluster has a membership of about 57 stars, the brightest of which are giants of the spectral type B0.