Arizona, United States
The Kitt Peak National Observatory (KPNO) is a United States astronomical observatory located on 2,096 m (6,880 ft) Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O'odham Nation, 88 kilometers (55 miles) southwest of Tucson. The observatory is considered to be part of the National Optical Astronomy Observatory (NOAO), although some of the telescopes located here, like those at the MDM Observatory, belong to other groups such as the University of Arizona's Steward Observatory. With 23 telescopes, it is the largest, most diverse gathering of astronomical instruments in the world.
Kitt Peak was selected in 1958 as the site for a national observatory under contract with the National Science Foundation (NSF) and was administered by the Association of Universities for Research in Astronomy. The land was leased from the Tohono O'odham under a perpetual agreement. In 1982 NOAO was formed to consolidate the management of three optical observatories – Kitt Peak, the National Solar Observatory facilities at Kitt Peak and Sacramento Peak, New Mexico, and the Cerro Tololo Inter-American Observatory in Chile.The observatory sites are under lease from the Tohono O'odham Nation at the amount of a quarter dollar per acre yearly, which was overwhelmingly approved by the Council in the 1950s. In 2005, the Tohono O'odham Nation brought suit against the National Science Foundation to stop further construction of gamma ray detectors in the Gardens of the Sacred Tohono O'odham Spirit I'itoi, which are just below the summit.
The principal instruments at KPNO are the Mayall 4 metre telescope; the WIYN 3.5 metre telescope and further 2.1 m, 1.3 m, 0.9 m, and 0.4 m reflecting telescopes. The McMath-Pierce Solar Telescope located on the facilities is the largest solar telescope in the world, and the largest unobstructed reflector (it doesn't have a secondary mirror in the path of incoming light). The ARO 12m Radio Telescope is also in the location.
Kitt Peak is also famous for hosting the first telescope (an old 91 cm reflector) used to search for near-Earth asteroids, and calculating the probability of an impact with planet Earth.
The Observatory also runs what it calls the Kitt Peak Advanced Observing Program (AOP) for advanced amateur astronomers.