Final answer:
Astronomers use charge-coupled devices (CCDs) as electronic detectors to record astronomical images. CCDs convert photons into a stream of charged particles, which are counted and stored as pixels. CCDs are similar to the detectors found in video camcorders and digital cameras.
Step-by-step explanation:
Astronomers use charge-coupled devices (CCDs) as electronic detectors to record astronomical images. This semiconductor chip converts photons of radiation into a stream of charged particles (electrons), which are stored and counted at the end of the exposure. Each counted part where the radiation hits the CCD is called a pixel, and modern CCDs can count the photons in millions of pixels (megapixels). CCDs are similar to the detectors used in video camcorders and digital cameras.