An observatory may also be an artificial satellite. Astronomers observe the various forms of radiation in space, including light, radio waves, and X rays. They also study how atoms behave in the vast spaces among the stars and in the high temperatures of the stars themselves. There are two chief kinds of observatories. Optical observatories have optical telescopes for the study of light.
Radio observatories have radio telescopes for the study of radio waves.
Optical telescopes use such devices as lenses and mirrors to form magnified images of distant objects. Most radio telescopes use large antennas to capture radio waves from space. Observatories also have such instruments as cameras and electronic sensors to record information gathered by optical and radio telescopes. In most cases, computers guide the telescopes and analyze the data they collect. Astronomers build observatories in places that have good observing conditions, free of such difficulties as those caused by violent atmospheric disturbances, polluted air, and bright lights.