What is a CCD camera ?
A CCD camera is, very simply, a digital camera. The CCD itself is a light-sensitive chip that is found in all digital cameras and camcorders, and also in computer webcams. These devices are normally used to take the single or multiple short exposures that make up digital photographs or digital videos. The chip consists of an array of pixels (picture elements). During an exposure, photons collide with pixels on the chip, and an electrical charge is built up. The amount of charge accumulated on a given pixel depends on how much light has hit that pixel during the exposure. Once the exposure is complete, information from the chip can be read by a computer and the picture displayed. Astronomical CCD cameras differ in several respects from off-the-shelf digital cameras. Astronomers like to record images of faint objects such as galaxies, requiring long exposure times, and astronomical CCD cameras are configured to allow this. One problem with long exposures and conventional CCD cameras is t
