Messier 12, M12, NGC 6218 Ophiuchus
M12 is a relatively small globular cluster in Ophiuchus discovered, but not resolved into stars, by Messier in 1764. The cluster is loosely packed with about 200,000 members, the brightest of which are magnitude 12, adding up to integrated apparent magnitude of 7.7. The cluster can be perceived in binoculars, but requires an 8 inch telescope for resolution. M12 is estimated to be 12.7 billion years old, 75 LY in diameter, and 23,000 LY distant, approaching at 16 Km/sec.
The attached, reprocessed image was taken with the TSAPO100Q astrograph, Sigma APO 1.4x tele-extender, Celestron AVX mount, unmodified Canon 600D camera, Astronomik CLS-CCD filter, and Orion 60mm F4 SSAGpro autoguider.
The image is a stack of only 2 x 240 sec exposures at iso 1600, processed with 30 dark and 30 bias frames, 2x drizzle, 25% crop. Limiting magnitude is 17.
Software used was PHD2, DSS, XnView, StarTools, and Neat Image.
Thank you for looking.