The difference is that astronomical sources like planets, stars, and galaxies are so far away that they are almost always too faint to study with typical photographic equipment. In astronomical telescopes, special optical components are therefore used to transmit as much light as possible—special CCDs are especially efficient in detecting light—and the entire camera assembly is cryogenically cooled to hundreds of degrees below zero Fahrenheit in a special container called a dewar. These measures help astronomers measure objects millions—even billions—of times fainter than would be possible with ordinary store-bought cameras.