Mount Wilson Observatory, astronomical observatory located in California on Mt. Wilson, near Pasadena. Mt. Wilson Observatory was founded in 1904 by George E. Hale. Its equipment includes 100-in. (2.5-m) and 60-in. (1.50-m) reflecting telescopes and two solar-tower telescopes 150 ft. (46 m) and 60 ft. (18 m) in length. The most recent addition is the CHARA ( C enter for H igh A ngular R esolution A stronomy) array operated by Georgia State Univ.; it consists of six 39-in. (1-m) aperture telescopes arranged in a Y-shape and contained in a 1,300-ft (400-m) diameter circle. When it becomes operational in 2000, the signals from the six telescopes will be combined and analyzed by a computer using optical interferometry techniques, producing the equivalent of the light-gathering power of a single telescope with a 1,300-ft (400-m) aperture. Principal research programs that have been conducted at the observatory include studies of the structure and dimensions of the universe and the physical nature, chemical composition, and evolution of celestial bodies. An ongoing program on the 60-in. telescope is a long-term study of singly ionized calcium lines to monitor sunspot cycles on nearby solar-type stars. The CHARA array will measure details of the surfaces of stars like the sun; the movements of double stars orbiting around each other and of planets orbiting distant stars; and planet formation around stars. The observatory, along with the Palomar Observatory (see under Palomar Mountain), was formerly part of the Hale Observatories, which were jointly administered by the California Institute of Technology and the Carnegie Institution. In 1986 the Carnegie Institution transferred the observatory's management to the newly formed Mount Wilson Institute.