M14: One of the many globular clusters in Ophiucus, in the general direction of the galactic center.
Right Ascension: 17h 37.6m
Declination: -3° 14.75'
Apparent Magnitude: 7.6
Date: June 2010
Telescope: Meade 16" Schmidt Cassegrain with f6.3 reducer (at ~f6)
Camera: SBIG ST-10XE
Exposure: (all binned 2x2)
R: 8x3 minutes
G: 7x3 minutes
B: 7x3 minutes
Camera temperature was -35°C
Processing Notes: Data acquisition with CCDSoft. Reduced and aligned in CCDStack. Subs combined in Sigma Beta. RGB combined in AstroArt with a ratio of 1:1.1:1.7 (from rough calculations to compensate for atmospheric extinction). Saved as a TIFF for import into Photoshop. Adjusted curves and levels. Slight Gaussian blur to reduce background noise. A couple of iterations of unsharp mask.
Additional Comments: This was a target of opportunity. The first quarter moon was out and this was in a different direction. We looked at a couple of other nearby globular clusters and this one had the most optimal guide star for guiding. This is one of the first images taken at the FLC observatory with the water cooling on the camera and the AO-8 "adaptive optics" used for autoguiding. Data acquisition by Pete Samuelson, processing by Charles Hakes.
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
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