The Very Red Stars of M13 (5-27-2011)

Last night I set up to image in H-alpha.  While waiting for my intended target to clear the trees, I took 4x8' of M13 in H-alpha.  This monochrome image records only a very narrow band of the deep red part of the spectrum.  I had no idea M13 was so red.  Half of the galaxy NGC 6207 can be seen in the upper right.  It, too, is apparently very red.

The camera was the Atik 16 and the filter is an Astronomik 6nm Profi H-alpha.  It is installed right next to the camera chip.  This image was taken with the Orion ST120 w/WO 0.8 ff/fr II, at f/4.