There are four broad categories of digital cameras that might reasonably be used for astrophotography. These are:
- Consumer compact cameras;
- Digital single-lens reflex cameras (DSLRs);
- Cooled astronomical CCD cameras; and
Consumer compact cameras have non-removable lenses, limited manual controls, and may not allow for very long exposure times. Any limitation of long exposure periods restricts their use for deep-sky work, but less demanding fields such as lunar and planetary imaging and scenic work may be possible.
DSLRs have interchangeable lenses and hence access to a wide range of focal lengths and adaptors that connect directly to specific telescopes. They are also extremely flexible, allowing the photographer to control manually virtually every significant setting - shutter speed, aperture, exposure mode, ISO setting, exposure compensation etc. When compared with consumer compact cameras they have much larger digital sensors. The best professional DSLRs have "full-frame" sensors - ie sensors the same size as the traditional 35mm film frames (36 x 24mm) and can therfore capture more photons.
Cooled astronomical CCD cameras are dedicated and specialized scientific instruments used by serious astrophotgraphers. The principal advantage of cameras of this type is that their CCDs are cooled to reduce "hot pixels" or noise created by heat within the CCD chip itself. They are designed specifically for use through a telescope and in conjunction with a computer. cameras of this type are generally expensive but suitable for deep-field work. They are obtainable from manufacturers such as Santa Barbara Instrument Group, Starlight Xpress, and Finger Lakes Instrumentation.
Webcams are typically inexpensive instruments designed, as the name suggests, to stream video over the web.The have small CCD or CMOS chips with very small pixels dimensions. Images are downloaded directly downloaded to connected computer and resolution is usually limited to 640 x 480 pixels or lower. They may be appropriate for lunar or planetary imaging, but are not suitable for deep-sky work.