User:DigitalC/sandbox/HOT

Roger Bacon described a telescope in the 13th century, however it is unknown whether he built a working model. There is documentary evidence, but no physical evidence, that the principles of telescopes were known in the late 16th century. By the early 17th century, use of telescopes became widespread in Europe. Galileo devoted his time to improving the telescope by increasing its power, and his were the first to be given the name "telescope". His first telescope magnified three diameters; but he soon made instruments which magnified eight diameters, and finally one that magnified thirty-three diameters.(DATE?). Johannes Kepler was the first to advance the idea of using two convex lenses and Christoph Scheiner was the first to construct a telescope of this form. The first reflecting telescope—a telescope using mirrors—is credited to Niccolò Zucchi in 1616.

Chester Moore Hall determined in 1733 that by combining two lenses formed from different types of glass, he could create an achromatic lense to reduce chromatic aberration. The development of the achromatic lenses led to a boom in the construction of large refracting telescopes in the late 19th century. In 1897 the refractor reached its maximum practical limit with the construction of the Yerkes Observatory's 40 inch (101.6 cm) refractor. The first giant reflecting telescope can be said to be William Herschel's great reflector with a mirror of 49 inches (124 cm) with a 40 ft (12 m) focal length built in 1789. The 20th century saw the construction of much larger reflecting telescopes such as Mount Wilson Observatory’s 60-inch (1.5 m) reflector in 1908 and the 100 inch (2.5 m) Hooker telescope in 1917.

The twentieth century saw the construction of telescopes which could image wavelengths other than visible light. The first radio telescope was built by Grote Reber in 1937, and telescopes were developed for other parts of the electromagnetic spectrum from radio to gamma-rays.