A CCD camera uses a small, rectangular piece of silicon rather than a piece of film to receive incoming light. This is a special piece of silicon called a charge-coupled device (CCD). This silicon wafer is a solid-state electronic component which has been micro-manufactured and segmented into an array of individual light-sensitive cells called "photosites." Each photosite is one element of the whole picture that is formed, thus it is called a picture element, or "pixel." The more common CCDs found in camcorders and other retail devices have a pixel array that is a few hundred photosites high by a few hundred photosites wide (e.g., 500x300, or 320x200), yielding tens of thousands of pixels. Since most CCDs are only about 1/4" or 1/3" square, each of the many thousands of pixels are only about 10 millionths of a meter (about 4 ten-thousandths of an inch) wide! The TTAS’s ST7-XE CCD has 765x510 pixels (390,150) in a area of 6.9mm wide by 4.6mm deep.

The CCD photosites accomplish their task of sensing incoming light through the photoelectric effect, which is a characterization of the action of certain materials to release an electron when hit with a photon of light. The electrons emitted within the CCD are fenced within nonconductive boundaries, so that they remain within the area of the photon strike. As long as light is allowed to impinge on a photosite, electrons will accumulate in that pixel. When the source of light is extinguished (e.g., the shutter is closed), simple electronic circuitry and a microprocessor or computer are used to unload the CCD array, count the electrons in each pixel, and process the resulting data into an image on a video monitor or other output media.

The difference between a CCD camcorder and an astronomical CCD camera is that a camcorder must take and display 60 sequential images per second to replicate motion and colour from daylight scenes, while an astronomical camera is used to take long-duration exposures (from many seconds up to a few hours long) of very dim starlight to replicate an apparently motionless object. Camcorders make colour images by merging the data taken simultaneously by groups of adjacent pixels covered by red, green, and blue filters. Astronomical CCD cameras also can make colour images, but these are made by post-exposure processing and merging of three separate exposures of an object made through red, green, and blue filters.