High Quality Content by WIKIPEDIA articles! The Cerro Tololo Inter-American Observatory (CTIO, IAU code 807) is a complex of astronomical telescopes and instruments located at 30.169 S, 70.804 W, approximately 80 km to the East of La Serena, Chile at an altitude of 2200 metres. The complex is part of the National Optical Astronomy Observatory (NOAO) along with Kitt Peak National Observatory (KPNO) in Tucson, Arizona. Dr. Nicholas U. Mayall was intimately involved in its creation.