Palomar Observatory, California

This observatory in the hills of Southern California opened in 1948, and for a long time was considered the best optical observatory in the world. Facilities include the 5.1-meter (200-inch) Hale telescope, the 1.2-meter (48-inch) Samuel Oschin Telescope, and a 1.5-meter (60-inch) telescope. As in many other early optical observatories located in the Southwest, light pollution from nearby growing cities and encroaching suburbs have decreased Palomar's effectiveness. Conversion to digital observation through the use of video CCDs, and the development of Adaptive Optics has helped to make Palomar a busier place however, and it is used now by Caltech, Cornell, and the Jet Propulsion Lab, among others.