M22 is a very remarkable object, one of the nearer globular clusters, lying
10,000 light years distant. The stars are spread over a region roughly 200 light
years in diameter, and receding from us at 144 km/sec. It is visible to the
naked eye, as it is brighter than the Hercules globular cluster M13 and outshined
only by the two bright southern globulars (not in Messier's catalog), Omega
Centauri (NGC 5139) and 47 Tucanae (NGC 104) - this is the ranking of the four
brightest in the sky.
I take this image through a Celestron 8 at f/3,3 on Pixcel 237 CCD. LRGB image
are composite of 4x30 second exposure of luminance layer and each of RGB component
3x30 second exposure.
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