<P> Developments of adaptive optics include systems with multiple lasers over a wider corrected field, and / or working above kiloHertz rates for good correction at visible wavelengths; these are currently in progress but not yet in routine operation as of 2015 . </P> <P> The twentieth century saw the construction of telescopes which could produce images using wavelengths other than visible light starting in 1931 when Karl Jansky discovered astronomical objects gave off radio emissions; this prompted a new era of observational astronomy after World War II, with telescopes being developed for other parts of the electromagnetic spectrum from radio to gamma - rays . </P> <P> Radio astronomy began in 1931 when Karl Jansky discovered that the Milky Way was a source of radio emission while doing research on terrestrial static with a direction antenna . Building on Jansky's work, Grote Reber built a more sophisticated purpose - built radio telescope in 1937, with a 31.4 - foot (9.6 m) dish; using this, he discovered various unexplained radio sources in the sky . Interest in radio astronomy grew after the Second World War when much larger dishes were built including: the 250 - foot (76 m) Jodrell bank telescope (1957), the 300 - foot (91 m) Green Bank Telescope (1962), and the 100 - metre (330 ft) Effelsberg telescope (1971). The huge 1,000 - foot (300 m) Arecibo telescope (1963) is so large that it is fixed into a natural depression in the ground; the central antenna can be steered to allow the telescope to study objects up to twenty degrees from the zenith . However, not every radio telescope is of the dish type . For example, the Mills Cross Telescope (1954) was an early example of an array which used two perpendicular lines of antennae 1,500 feet (460 m) in length to survey the sky . </P> <P> High - energy radio waves are known as microwaves and this has been an important area of astronomy ever since the discovery of the cosmic microwave background radiation in 1964 . Many ground - based radio telescopes can study microwaves . Short wavelength microwaves are best studied from space because water vapor (even at high altitudes) strongly weakens the signal . The Cosmic Background Explorer (1989) revolutionized the study of the microwave background radiation . </P>

Who invented the telescope and when was it invented