Galileo greatly improved upon this design the following year. In 1668, Isaac Newton designed an improved a reflecting telescope that bears his name, the “Newtonian reflector. These were credited to three individuals: Hans Lippershey and Zacharias Janssen, who were spectacle-makers in Middelburg, and Jacob Metius of Alkmaar—also known as Jacob Adriaanszoon. “. Niccolò Zucchi is credited with constructing the first reflecting telescope in 1616. Although there were some recorded instances of pre-17th century Middle Eastern and European opticians—such as Leonard Digges, Taqi al-Din and others—creating devices that could have functioned as telescopes, the earliest known working telescopes were the refracting telescopes that appeared in the Netherlands in 1608
The first known practically functioning telescopes were invented in the Netherlands at the beginning of the 17th century. The name “Telescope” was coined by an unidentified Greek poet/theologian who was present at a banquet held in 1611 by Prince Federico Cesi and the name was given to a version of the instrument constructed by Galileo Galilei. A telescope is an instrument designed for the observation of remote objects and the collection of electromagnetic radiation. “Telescopes” can refer to a whole range of instruments operating in most regions of the electromagnetic spectrum
Radio telescopes are directional radio antennas that often have a parabolic shape. As of 2005, the current record array size is many times the width of the Earth—utilizing space-based Very Long Baseline Interferometry telescopes such as the Japanese HALCA VSOP satellite. Radio telescopes are also used to collect microwave radiation, which is used to collect radiation when any visible light is obstructed or faint, such as from quasars. One particularly exciting example is the Wow! signal, recorded in 1977. Aperture synthesis is now also being applied to optical telescopes using optical interferometers and aperture masking interferometry at single reflecting telescopes. Multi-element Radio telescopes are constructed from pairs or larger groups of these dishes to synthesize large ‘virtual’ apertures that are similar in size to the separation between the telescopes; this process is known as aperture synthesis. Some radio telescopes are used by programs such as SETI and the Arecibo Observatory to search for exterrestrial life. The dishes are sometimes constructed of a conductive wire mesh whose openings are smaller than the wavelength being observed
The name “telescope” covers a wide range of instruments and is difficult to define. The most common type is the optical telescope; other types also exist and are listed below. They all have the attribute of collecting electromagnetic radiation so it can be studied or analyzed in some manner
The first radio telescope went into operation in 1937. Since then, a tremendous variety of complex astronomical instruments have been developed. The 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays
An optical telescope gathers and focuses light mainly from the visible part of the electromagnetic spectrum . Optical telescopes are used for astronomy and in many non-astronomical instruments, including: theodolites , spotting scopes, monoculars, binoculars, camera lenses, and spyglasses. Optical telescopes increase the apparent angular size of distant objects as well as their apparent brightness. There are three main types:. In order for the image to be observed, photographed, studied, and sent to a computer, telescopes work by employing one or more curved optical elements—usually made from glass—lenses, or mirrors to gather light and other electromagnetic radiation to bring that light or radiation to a focal point
These types of telescopes are usually on Earth-orbiting satellites or high-flying balloons since the Earth’s atmosphere is opaque to this part of the electromagnetic spectrum. Gamma-ray telescopes refrain from focusing completely and use coded aperture masks: the patterns of the shadow the mask creates can be reconstructed to form an image. X-ray and gamma-ray radiation go through most metals and glasses, but some X-ray telescopes use Wolter telescopes composed of ring-shaped ‘glancing’ mirrors made of heavy metals that are able to reflect the rays just a few degrees. The mirrors are usually a section of a rotated parabola and a hyperbola, or ellipse
Reflecting telescopes, though not limited by the color problems seen in refractors, were hampered by the use of fast tarnishing speculum metal mirrors employed during the 18th and early 19th century—a problem alleviated by the introduction of silver coated glass mirrors in 1857, and aluminized mirrors in 1932. The maximum physical size limit for refracting telescopes is about 1 meter , dictating that the vast majority of large optical researching telescopes built since the turn of the 20th century have been reflectors. The invention of the achromatic lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter, higher functioning refracting telescopes