^BCerro Tololo observatory. ^b 360-degree panoramic view of the telescope domes at the Cerro Tololo Inter- American Observatory (CTIO) near La Serena, Chile. The seven largest domes are (from left to right): 40- centimetre (16-inch) telescope; 1. 2 metre radio telescope; Yale 1 metre telescope; Curtis-Schmidt telescope; 4 metre Victor Blanco telescope; 1. 5 metre Ritchey-Chretien telescope; and the 0. 9 metre telescope. The high altitude of Cerro Tololo (2200 metres), & the clear air above it, are ideal for the observatory because atmospheric distortions to incoming light are reduced. In 1997 Cerro Tololo is operated by the National Optical Astronomy Observatories (NOAO).