Ring Nebula 1k x 1k E2V 47-10

I was fortunuate to borrow an Apogee Alta U47 locally from Apogee instruments and doubly fortunate to image on Ken Crawford’s 20" RCOS RC in the nearby dark skies in Camino, CA at his Rancho del Sol Observatory.  I have not used high efficiency back-thinned CCDs before.  This E2V 47-10 is a 1k x 1k 13 mic pixel CCD with ~90% quantum efficiency across the visible spectrum.  We used Astrodon E-Series LRGB filters. A G2V star measurement resulted in color weight ratios of 1.0:1.0:1.1.  Sky flats with CCDAutoPilot 2.55 and darks were taken. Calibrated in CCDStack and processed in Photoshop CS.  I wanted to see if I could bring out the halo surrounding the Ring Nebula that others, including me, have produced with the assistance of H-a filters.  This was only an LRGB image with no H-a and only 21 min of each color. I did take the liberty of differentially stretching the halo to bring it out and the use of some high-pass sharpening.  So, this was an experiment as a first light (for me) with a back-thinned CCD camera. It was operated at -25C and only required about 50% power.