Mount Wilson Hooker Telescope dome. This dome houses an optical telescope called the Hooker Telescope, named after a benefactor when it was built in 1917. At about 2.5 metres (100 inches), it was the largest telescope in the world until 1948. Many important advances in astronomy took place here, including Hubble's pioneering observation of the redshift of distant galaxies. The telescope was inactive between 1986 and 1994, but has been upgraded and is now being used for further astronomical research. This dome is part of the Mount Wilson Observatory, which sits at an elevation of 1742 metres within the San Gabriel mountain range in California, USA.