Keck TelescopesTwo 10-meter diameter Ritchey–Chrétien telescopes housed at the W.M. Keck Observatory on Mauna Kea in Hawaii. Built and operated by the California Association for Research in Astronomy (CARA), an organization whose Board of Directors includes representatives from the California Institute of Technology and the University of California, they are the world's largest reflecting telescopes, operating at optical and infrared wavelengths. The establishment of both the telescopes and the observatory was made possible by grants from the W.M. Keck Foundation. The first telescope, Keck I, was completed in 1992 and became operational in May 1993. Keck II was constructed 85 meters away, making it possible for the pair to be used as an optical interferometer; it began working as a science instrument in October 1996.
Both telescopes have a segmented primary mirror (f/1.75) composed of 36 hexagonal segments, each 1.8 meters across and made of Zerodur. In each case, the assembly is controlled with active optics. Interchangeable secondary mirrors allow optical or infrared observations at either a Cassegrain or two Nasmyth foci. The telescopes are also equipped with several spectrographs and spectrometers for operation in the visible (0.3–1 μm), near-infrared (1–5 μm), and mid-infrared (5–27 μm) wavebands.
In 1996, NASA joined CARA in running the W.M. Keck Observatory and made the observatory a cornerstone of its Origins program.