M13 The Great Cluster

Without doubt the finest of globular clusters visible in the northern hemisphere. Located outside the plane of our galaxy and some 25,000 light years away.

An easy target to find.

M13 is located in the constellation Hercules, between summertime’s two brightest stars, Vega and Arcturus. About 1/3 of the way from Vega to Arcturus, locate the four modestly bright stars forming the Keystone of Hercules. On the Arcturus side of the Keystone, M13 lies between the stars Eta Herculis and Zeta Herculis.

A typical binocular field is about 5 to 7 degrees in diameter, and the Hercules cluster is found about 2.5 degrees south of Eta Herculis. The Hercules cluster’s position is Right Ascension: 16h 41.7m; Declination: 36 degrees 28′ north.

M13 was one of my first targets I captured many years ago. The cluster will not have changed since it's discovery over 300 years ago,  but my imaging and processing have. This Image is just 1.5 hours of data using the ZWO RGB filters, 30 minutes per filter.

Cropped image

Processed in Pixinsight.

M13

A test of the set up was required. So I rebalanced and ran PHD of a target much lower in declination than M106. I wanted something bright and easy so M13 was an easy choice to make rising nicely in the North east. I ran the guide programme for 5 minutes with no issues. Fingers were crossed and I ran 5 x 20 minute exposures as a test run really. Calibrated in Maxim DL and processed in photoshop. All I done to process was levels and curves. No unsharp masks or colour correction. Very pleased the core of the structure was not overcooked. A close inspection of the image had shown a faint galaxy between M13 and NGC6207. Carte Du Ceil shows it to be a PGC (principle galaxy catalogue) designation PGC2085277 a mag16.15 galaxy some 2500 times further away than the galactic cluster M13. Delving deeper I found 31 in total as deep as 19.22. Some showing as a marginal brigtening of a pixel or 2 but still there. call up a 2 degree FOV in Carte du Ceil and see how many you can capture too. You may have to download a few extra catalogues though.