This is a magnitude 9.5 open cluster in Lyra that resembles more a globular than it does a normal open cluster. Consisting mainly of ancient yellow stars in the cluster itself, you see a sprinkling of younger blue stars in the foreground. This cluster is less than 1 degree SEE of Theta Lyra. From the APOD Site: NGC 6791 is one of the oldest and largest open clusters of stars known. But how did it get so dirty? Open star clusters usually contain a few hundred stars each less than a billion years old. Open star cluster NGC 6791, however, contains thousands of stars recently measured to be about 8 billion years old. Whats really confusing, though, is that the stars of NGC 6791 are relatively dirty - the minuscule amounts of heavy elements (generically called metals) are high relative to most other star clusters. Older stars are supposed to be metal poor, since metals have only been slowly accumulating in our Milky Way Galaxy. This enigma makes NGC 6791, pictured above, one of the most studied open clusters and a possible example of how stars might evolve in the centers of galaxies. Taken: - 6/16/2006 Conditions: - Transparency very poor, seeing about 5 (very poor night...but the first opportunity to image in weeks due to rain, so I coudnt resist.) Equipment: - TOA-150 - Paramount ME - SBIG ST-2000XM, self-guided - ST CFW-10, Astrodon LRGB filters - FLI PDF Exposures: (74 minutes so far) - L = 9x2mins - R = 10x2mins - G = 9x2mins - B = 9x2mins Processing: CCDStack: - initial sub registration - RGB combine, used to generate synthetic luminance (Ls) - Ls mean combined with the natural L - Deconvolution (Positive Constraint, 25 runs) - DDP - LsLRGB combine PSCS2: - gradient control (see my gradient control tip in the tips and tricks section) - noise control (NeatImage) - slightly increased hue and saturation (Interestingly enough, I did NO increased saturation on the bright orange star in the upper left!) - curves to bring up the mid-tones - slight sharpening via Smart Sharpen in PSCS