M2: Globular cluster in the constellation Aquarius.
Right Ascension: 21h 33m 27s
Declination: 0° 49'
Apparent Magnitude: 6.3
Date: July 2009
Telescope: Meade 16" Schmidt Cassegrain with f6.3 reducer
Camera: SBIG ST-10XE
Guiding: Meade 5" refractor/DSI Pro/PHD
Exposure: L: 5x2 minutes
Processing Notes: Data acquisition with CCDSoft. Reduced and aligned in CCDStack (using 3 minute darks). Subs combined in Sigma Beta. Arcsine import into Photoshop. Adjusted curves and levels. Slight Gaussian blur, more on the dim areas, and some sharpening on the bright areas.
Links to images of this object on other sites:
Additional Comments: This is one of the "lost" images from 2009. Processing was never done during summer 2009 when the image was taken, and I am not sure who did the imaging. (Possibly because there was not a set of 2 minute darks?) Processing 4/17/2010 by CLH.
The name "globular" cluster, coined by William Hershel, is very descriptive of their appearance - a glob of stars. There are fewer than 200 globular clusters known around the Milky Way, and unless you are familiar with specific ones, they all look very similar. These clusters condensed while the Milky Way was still forming, and reside in a spherical halo around the disk. Unlike objects in the disk, which have a mostly orderly rotation about the galactic center, the orbits of globular clusters are random. It was the three dimensional distribution of globular clusters that Harlow Shapely used to find the center of the Milky Way. All large galaxies are observed to have globular clusters in a halo. Globular clusters are ancient. Generally comprising what are called Population II stars (old ones with fewer heavy elements), there are no longer any luminous, blue, main sequence stars, and the remaining distribution of stars is noticeably redder than that found in open clusters in the spiral arms. Lots more information can be found here: http://en.wikipedia.org/wiki/Globular_cluster