M22 - The Sagittarius Globular
Probably the first globular cluster ever discovered, by A. Ihle in 1665.

  • RA: 18:36
  • Dec: -23:54
  • Size: 24'
  • Magnitude: 5.1
  • Distance: 10,100 ly
  • Constellation: Sagittarius
  • Millennium Star Atlas: Vol. III, p. 1391
  • Scope: 12.5" Ritchey-Chretien at f/9
  • Autoguider: ST-4 in average mode
  • Sky conditions: Good transparency, excellent seeing
  • Film: FLI Dream Machine CCD
  • Exposure: 16x90 seconds L, 4x240 seconds R,G,B
  • Date: 7-24-03

A nearby globular, outshone in brightness only by two southern hemisphere globulars, the Omega Centauri and 47 Tucanae clusters. The image itself turned out pretty passably, especially considering I chased it down to ten degrees off the horizon for the final red channel frame. Not surprisingly, getting rid of the extinction and index of refraction effects was a bit of a challenge.

Note: image upsized to 133 percent of original size to highlight cluster detail.


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