Messier 13 (M13, NGC 6205), known as the 'Great Globular Cluster' in the constellation Hercules', is a well-known celestial object in the late Spring and Summer sky. It can be seen with the naked eye if the observer is at a dark sky location.

It is a member of a swarm of globular star clusters that orbit our Milky Way galaxy. A globular star cluster gets its name because it has a large center concentration ( a glob) of stars. M13 has hundreds of thousands of stars and measures about 150 light years in diameter and is about 25,000 light years from us.

M13 was discovered in 1714 by the comet discoverer Edmond Halley. In 1974, it was selected as the target for one of the first radio messages sent to possible extra-terrestrial intelligent races by the giant, in-ground radio telescope at the Arecibo Observatory in Puerto Rico.



Dates taken:
May 20 and 21, 2009
Location:
Ft. Griffin State Historic Site, Texas
Telescope:
Astro-Tech 6" Ritchey-Chretien at f/9 1370mm focal length
Mount:
Takahashi EM-11 Temma 2, guided by an SBIG ST-237 thru an E-finder at 100mm focal length
Camera:
Canon XSi, at prime focus; modified by Hap Griffin with the Baader filter
Camera Control and Focusing:
ImagesPlus 3.60 (IP)
Exposures:
28 at 5 minutes each; 40 at 2 minutes each; 10 at 1 minute each; all at ISO 800 in Raw mode
Total Exposure time:
3 hours 50 minutes
Processing:
Converted, calibrated, de-bayered, normalized, aligned and MinMax combined
using Automatic Image Set Processing and deconvolution in IP.
Final processing in Photoshop CS2

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