What are their limitations for Astronomical use?
Digicams were not designed with astronomical imaging in mind! However, amateur astronomers can take advantage of certain special features they offer. Exposures are limited to a maximum of few tens of seconds, and often less than 5 seconds, which means that faint objects cannot be recorded. With long (i.e. greater than a few seconds) exposures the major limitation is digital ‘noise’ in the image. Some of this noise (but not all) can be removed during image processing. CCD cameras specifically designed for Astronomy are electronically cooled to reduce this noise. Additionally, apart from a very few models, digicams have non-removable lenses which means they cannot be used at the Prime Focus of a telescope. Eyepiece-projection (Afocal Projection) is therefore the only option for recording an image through an astronomical telescope.
