Exploring the expanding Universe The Hale telescope on Mt. Palomar in southern California was built to see further and to see finer detail than the Hooker 100 inch. It has a mirror that is 200 inches (5 metre) across. It gathers four times more light than the Hooker. When opened in 1948, it was the the largest optical telescope in the world. In the image, some of the four hundred guests present at the opening ceremony can be seen seated under the telescope.