Cerro Tololo Inter-American Observatory (sāˈrō tōlōˈlō) [key], astronomical observatory located on Cerro Tololo peak, Chile, with offices in La Serena, about 40 mi (64 km) to the west. Funded by the U.S. National Science Foundation (NSF), it is operated by the Association of Universities for Research in Astronomy (AURA), which also operates such other major national observatories as the Kitt Peak National Observatory in Arizona. The principal instrument is a 158-in. (4-m) reflecting telescope, the largest in the Southern Hemisphere and the twin of the 158-in. (4-m) reflector at Kitt Peak. Other equipment of the observatory includes 60-in. (1.5-m), 36-in. (0.9-m), and twin 16-in. (0.4-m) reflectors and the 24-in. (0.6-m) Curtis-Schmidt camera formerly at the Univ. of Michigan. Also at Cerro Tololo, a half mile from the summit, is a 24-in. (0.6-m) reflector belonging to the Lowell Observatory. Additional telescopes are planned for the 1990s, including a 161 in. (4.1-m) telescope from Columbia Univ. and a new 26-ft (8-m) reflector.