ASTR 209 Lecture Notes - Lecture 4: Photon Counting, Photographic Film, Pixel

• School: University of Calgary
• Department: Astronomy
• Course: ASTR 209
• Professor: J.Still

Document Summary

Detectors in astronomical telescope, charge coupled device (ccd, electronic cameras contain a charge coupled device (ccd, a ccd is a light-sensitive chip, usually less than 1cm in size. Advanced astronomical ccds are about 10 cm in size and very carefully manufactures. Photographic film relies on a chemical reaction indicated by light: ccds are more sensitive than photographic film, especially in low- light conditions, ccds can be used in space observations, a ccd is an array of photon counters. Little buckets: water dripping example, each pixel records how many photons arrived over the exposure time, ccds are often identified by their number of elements (pixels). For example, a 5 megapixel ccd has 5 million pixels (approximately 2250 pixels on a side: each pixel in a ccd records how many photons it received, every photon releases an electron that stays inside the pixel.