M12 (NGC 6218) is a Shapley-Sawyer class IX (http://en.wikipedia.org/wiki/Shapley%E2%80%93Sawyer_Concentration_Class) globular cluster located approximately 15,700 light-years away in Ophiuchus.
Luminance – 15x600s – 180 minutes – binned 1x1
RGB – 8x300s – 40 minutes each – binned 2x2
270 minutes total exposure – 4 hours 30 minutes
Imaged from Dardenne Prairie, Missouri (a red zone) over four nights in March, April, May and June, 2017 with a SBIG ST-8300M on an Astro-Tech AT90EDT at f/6.7 603mm.
LRGB - https://www.flickr.com/photos/dcrowson/35002891084/sizes/l