From: PetaPixel

[youtube=http://www.youtube.com/watch?v=p5c1XoL1KFs]

Those epic photographs of stars and galaxies that you see on sites like NASA’s Astronomy Picture of the Day don’t actually look like that straight out of the camera. Instead, a good deal of post-processing magic goes into each photograph. How much magic? Countless black and white photographs shot with different cameras are carefully weaved together, and color is added to enhance the final image. The video above gives a quick and interesting two minute tour of how they post-processed one particular photo in Photoshop.