From HubbleSiteChannel
While we’re on the subject of space, have you ever wondered how the images of far away galaxies captured by space telescopes, such as the Hubble Telescope, are “created?” Start with black and white images, process them, rotate them, overlay them, then finally, colorize. Interestingly, the bad pixels are cleaned… I wonder how they can tell from the millions of points of light which are bad pixels and not a far away star.