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The 100-inch Hooker Telescope

Mount Wilson's 100-inch Telescope dome in the early days(photo courtesy the Huntington Library).

The Hooker 100-inch telescope is named after John D. Hooker, who provided the funds for the giant mirror. It was the largest telescope in the world from 1917 to 1948 when the 200-inch telescope was built on Palomar Mountain 90 miles to the southeast. Many great discoveries were made with the 100-inch telescope, including Edwin Hubble's landmark work on the expansion of the Universe and the establishment of the cosmic distance scale. The first optical interferometer ever used for astronomical research was used on the 100-inch telescope to measure the sizes of distant stars for the first time in 1919.

Mount Wilson's 100-inch Telescope (photo by David Jurasevich).

The 100-inch telescope has three optical configurations available to meet the requirements of a wide variety research projects. A very high-resolution spectrograph is located at the telescope's Coudé focus. Located on the ground floor of the 100-inch telescope dome, the Aluminizing Room is used to recoat all of the telescope mirrors at the observatory.

The telescope was inactive from 1986 to 1994. It subsequently underwent major upgrades to its control systems to make it once again available for scientific research, although great care was taken to preserve elements of its history. A state-of-the-art adaptive optics system was developed to enable new high-resolution studies of astronomical objects. This and other important additions to the telescope keep the 100-inch well prepared for research in the 21st century.

Although the 100-inch is not open for public viewing, it is an ideal instrument for experimental and long-term research programs. In recent years, astronomers from Caltech, the Smithsonian Institution, the Jet Propulsion Laboratory, the University of Illinois, and the U.S. Naval Observatory have carried out a variety of projects on the telescope.

The telescope, which is a National Mechanical Engineering Landmark, is accessible to the public during the daytime by means of a visitors gallery entered on the west side of the 100-inch telescope dome.