Figure 2-27 RIVUXG Charge-Coupled Devices (CCDs) and Imaging (a) The 40 CCDs in this mosaic are used to record the light gathered by the Canada-France-Hawaii Telescope (see Figure 2-28). After an exposure, data from each of the 377 million light-sensitive pixels in the mosaic are transferred to a waiting computer. (b) This negative print (black stars and white sky) shows a portion of the sky as imaged with a 4-m telescope and photographic film. (c) This negative image of the same region of the sky was made with the same telescope, but with the photographic film replaced by a CCD. Many more stars and galaxies are visible. (d) To produce this color positive view of the same region, sequences of CCD images were made using different color filters. These were then combined using a computer image-processing program.