The 5m mirror for the telescope on Mt Palomar, California, on its grinding and polishing machine. The image was taken in 1934 when the casting of 65 tons of molten pyrex was made. The project for the construction of the Palomar observatory was led by the American astrophysicist George Hale (1868-1938). In 1929 he convinced the Rockefeller Foundation to donate six million dollars for building the 5m telescope. The first mirror made from fused quartz proved to be a failure. Hale next tried pyrex and the first experimental disc cast proved satisfactory. The grinding of the mirror was interrupted by the war and the telescope was finally completed in December 1947.