Image 1 Caption: The Leviathan of Parsonstown (reflector, primary diameter 1.83 m = 6 ft, operational 1845--c.1890) was the record largest telescope (i.e., the telescope with the largest primary) until 1917 when it was superpassed by the Hooker telescope (reflector, primary diameter 2.54 m = 100 in, operational 1917--present) at Mount Wilson Observatory in California (see Wikipedia: Timeline of telescopes, observatories, and observing technology: 1800--present).