McDonald Observatory, observatory founded in 1939 by the University of Texas, on the legacy of the Texas financier William J. McDonald, on Mount Locke near Fort Davis, Texas. The observatory includes the original 208-cm (82-inch) reflector, for many years the world’s second largest telescope; a 272-cm (107-inch) reflector, dedicated in 1968; two smaller reflectors; and the 920-cm (362-inch) Hobby-Eberly Telescope, a telescope that only moves in azimuth.
The observatory, which until 1963 was operated under a joint agreement with the University of Chicago, has been directed by such noted astronomers as Otto Struve, Gerard Kuiper, Bengt Strömgren, W.W. Morgan, and Harlan J. Smith. Discoveries credited to the observatory include those of Nereid, a satellite of Neptune, and Miranda, a satellite of Uranus. Principal research has emphasized stellar composition and evolution and the properties of external galaxies. Other research specialties include high-speed photometry and lunar laser and satellite ranging.