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)
Nançay radio telescope Nançay radio telescope The Nançay decimetric radio telescope (Le radiotélescope décimétrique de Nançay (NRT)) is located in the small commune of Nançay, two hours' drive south of Paris, France. The radio telescope saw first light in 1965, after an inauguration by the then French president, Charles de Gaulle. It is one of the largest radio telescopes in the world. The NRT is a transit instrument of the unusual Kraus-type design, with two mirrors. The flat, tilting primary mirror consists of ten panels, each 20 m long and 40 m (131 ft) high; it reflects radio waves towards the fixed secondary