History of the telescope a wider field of view than a classic Cassegrain. During the period 1850–1900, reflectors suffered from problems with speculum metal mirrors, and a considerable number of "Great Refractors" were built from 60 cm to 1 metre aperture, culminating in the Yerkes Observatory refractor in 1897; however, starting from the early 1900s a series of ever-larger reflectors with glass mirrors were built, including the Mount Wilson 60-inch (1.5 metre), the 100-inch (2.5 metre) Hooker Telescope (1917) and the 200-inch (5 metre) Hale telescope (1948); essentially all major research telescopes since 1900 have been reflectors. A number of 4-metre class (160 inch)
Bok Telescope Bok Telescope The Bok Telescope (also known as the 90-inch) is the largest telescope operated solely by Steward Observatory. It finds much use from astronomers from University of Arizona, Arizona State University, and Northern Arizona University, with instruments capable of both imaging and spectroscopy. The telescope operates year-round, except during the August summer-shutdown when maintenance is performed while the weather is poor (Arizona's monsoon season lasts from roughly July through August). The Bok Telescope was named after the prolific astronomer and director of Steward Observatory from 1966–1969, Bart Bok, one of the most beloved astronomers in Tucson. It was used