Palomar Observatory is a privately owned observatory in San Diego County, California, 90 miles (145 km) southeast of Mount Wilson Observatory, on Palomar Mountain in the Palomar Mountain Range. It is owned and run by the California Institute of Technology (Caltech). The observatory is made up of four main telescopes: the 200 inch (5.08 m) Hale telescope, the 48 inch (1.22 m) Samuel Oschin telescope, the 18 inch (457 millimeter) Schmidt telescope, and a 60 inch (1.52 m) reflecting telescope. Also, the Palomar Testbed Interferometer is located at this observatory.