The Hale Telescope is a 200-inch (5.1 m), f/3.3 reflecting telescope at the Palomar Observatory in California, US, named after astronomer George Ellery Hale. With funding from the Rockefeller Foundation, he orchestrated the planning, design, and construction of the observatory, but did not live to see its commissioning. The Hale was groundbreaking for its time, with double the diameter of the next largest telescope and pioneering the use of many technologies such as vapor deposited aluminum and low thermal expansion glass. It is still in active use.
It was the largest-aperture optical telescope in the world from its completion in 1948 until the BTA-6 was built in 1976, and the second largest until the construction of the Keck 1 in 1993.