CCDStack, Photoshop CS w/ the Fits Liberator plugin,
Carboni's actions and Russ Croman's Gradient Exterminator
CCDStack to register,
normalize, data reject, combine sub exposures, pixel math and RGB
combine. eXcalibrator (pre-beta) for color calibration.
luminance processing and LRGB combine.
North is to the top.
The M12 globular
cluster, NGC 6218, is in the constellation Ophiuchus and was
discovered by Charles Messier on May 30, 1764. The cluster is 16,000
light-years from Earth and has a spatial diameter of about 75
light-years. It is loosely packed and was once thought to be a
tightly concentrated open cluster. M12 has thirteen variable stars.