About this Image
M13, also called the `Great globular cluster in Hercules', is one of the most prominent and best known globulars of the Northern celestial hemisphere.
At its distance of 25,100 light years, its angular diameter of 20' corresponds to a linear 145 light years. It contains several 100,000 stars, most of them very old.
Towards its center, stars are about 500 times more concentrated than in the solar neighborhood. Older stars appear yellow, hotter stars appear blue.
16" cassegrain in secondary focus at f/10
|Camera||SBIG STL-11000M at -25C, internal filter wheel|
|Date||Apr 02, 2005.|
|Sky Conditions||mag 5 sky, raw FWHM 1.8-2", temperature 5 C|
|Exposure||L:R:G:B = 40:20:20:20 minutes (10-minute sub-exposures for RGB, 5 min subs for L),|
Image aquisition in Maxim, image calibration, aligning, DDP in ImagesPlus; color balance, curves, unsharp mask in Photoshop; Noise reduction by Neatimage;
north is up;