Palomar Mountain is located NE of San Diego, in Cleveland National Forest.

It is the site of the Palomar Observatory, operated by the California Institute of Technology. The Hale telescope there, completed in 1948 and named for its creator George E. Hale, was the world's largest reflecting telescope (200 in./508 cm) until 1976, when Soviet scientists constructed an even bigger one.

www link :
History of the Telescope