One problem with CCD cameras is that they tend to pick up "dark current," sometimes referred to as dark noise or thermal noise. The source of this signal is the infrared radiation from within the camera body. The warmer the camera is, the more dark current you see in images. If the camera is cooled down, the radiation is less severe. For this reason, the camera has a built in thermo-electric cooler (TEC). It generally can take the camera 30º Celsius below ambient temperature.
    Even with the cooling, images still show a salt-like smattering of bright pixels. Fortunately, this can all be subtracted out because there is a definite pattern. Unlike regular noise, the dark current can be repeated with a "dark frame" where an image is taken with the aperture closed. This picture is subtracted from the raw image. This procedure is detailed in the post-processing section.