The Hale’s main mirror was made by Corning Glass Works out of borosilicate glass (Pyrex). The voids you see in the model are to reduce the weight of the mirror; the first time Corning tried to cast the mirror, the refractory brick used to form the voids came loose and the mirror had to be scrapped — an embarrassing failure for Corning’s PR department, which had arranged for press coverage of the event.
200 inches is 5080 mm; the practical limit for a one-piece glass mirror like this is about 8.6 meters (achieved by the optical lab at the University of Arizona). All larger telescopes (like the Hale’s younger sister, the Keck, in Hawaii) use multiple mirrors which are automatically computer-aligned in real time.
The Hale’s main mirror was made by Corning Glass Works out of borosilicate glass (Pyrex). The voids you see in the model are to reduce the weight of the mirror; the first time Corning tried to cast the mirror, the refractory brick used to form the voids came loose and the mirror had to be scrapped — an embarrassing failure for Corning’s PR department, which had arranged for press coverage of the event.
200 inches is 5080 mm; the practical limit for a one-piece glass mirror like this is about 8.6 meters (achieved by the optical lab at the University of Arizona). All larger telescopes (like the Hale’s younger sister, the Keck, in Hawaii) use multiple mirrors which are automatically computer-aligned in real time.
