As a matter of fact, NASA prepares in Photoshop its gorgeous pictures from images taken by the Hubble space telescope. And, within two minutes, you can watch exactly how they do it. I would recommend to run it in slow motion if you really want to catch all the details and each and every step, but it’s worth it…
YouTube link
See also http://hubblesite.org/gallery/behind_the_pictures/ where you can see the same video in very high quality.