History of the telescope
The earliest known telescope appeared in 1608 in the Netherlands when an eyeglass maker named Hans Lippershey tried to obtain a patent on one. Although Lippershey did not receive his patent, news of the new invention soon spread across Europe. The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo improved on this design the following year and applied it to astronomy. In 1611, Johannes Kepler described how a far more useful telescope could be made with a convex objective lens and a convex eyepiece lens and by 1655 astronomers such as Christiaan Huygens were building powerful but unwieldy Keplerian telescopes with compound eyepieces.
History of the telescope
The next major development came in 1946 when Ryle and Vonberg (Ryle and Vonberg 1946) located a number of new cosmic radio sources by constructing a radio analogue of the Michelson interferometer. The signals from two radio antennas were added electronically to produce interference. Ryle and Vonberg's telescope used the rotation of the Earth to scan the sky in one dimension. With the development of larger arrays and of computers which could rapidly perform the necessary Fourier transforms, the first aperture synthesis imaging instruments were soon developed which could obtain high resolution images without the need of a giant parabolic reflector to perform the Fourier transform. This technique is now used in most radio astronomy observations. Radio astronomers soon developed the mathematical methods to perform aperture synthesis Fourier imaging using much larger arrays of telescopes —often spread across more than one continent. In the 1980s, the aperture synthesis technique was extended to visible light as well as infrared astronomy, providing the first very high resolution optical and infrared images of nearby stars.