M3 (NGC 5272) is a Shapley-Sawyer class VI (http://en.wikipedia.org/wiki/Shapley%E2%80%93Sawyer_Concentration_Class) globular cluster located approximately 34,000 light-years away in Canes Venatici.
Luminance – 24x600s – 240 minutes – binned 1x1
RGB – 8x300s – 40 minutes each – binned 2x2
360 minutes total exposure – 6 hours
Imaged February 29th, March 16th and 31st, 2016 from Rancho Hidalgo (Animas, New Mexico) with a SBIG STF-8300M on an Astro-Tech AT12RCT at f/8 2432mm.
LRGB - https://www.flickr.com/photos/dcrowson/25752178963/sizes/l