M23

  
 
 
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  • RA: 17:56.8
  • Dec:  -19:01
  • Magnitude: 6.9
  • Size: 27 arc min
  • Distance: 2,150 ly
  • Constellation:  Sagittarius
  • Scope: 8" SCT at f/10
  • Autoguider: ST-4 faint mode
  • Sky conditions: good seeing and transparency.
  • Film: Kodak Supra 400
  • Exposure: 24 minutes
  • Date:  July 12, 2004
  
 
Comments:   The night was warm and quite humid with a low about 65 and calm.  I even had a layer of ground fog for about 30 minutes a little after midnight.  The exposure was cut off at 24 minutes because the guide star was lost for unknown reasons.  M23 was discovered by Messier on June 20, 1764.  The diameter of the cluster is about 15 light years.  The age of the open cluster has been estimated to be about 220 to 300 million years.