Telescope: Difference between revisions
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The history of the telescope dates back to the Middle Ages, when [[Ibn al-Haytham]], [[Robert Grosseteste]] and other scientists studied magnifying properties of lenses. Although there were some recorded instances of pre-17th century [[Middle East|Middle-Eastern]] and [[Europe]]an opticians including [[Leonard Digges]], [[Taqi al-Din]] and others creating devices that could have functioned as telescopes, the earliest known working telescopes in the modern sense were the [[refracting telescope]]s that appeared in the [[Netherlands]] in [[1608]]. 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. [[Galileo Galilei|Galileo]] greatly improved upon this design the following year. [[Niccolò Zucchi]] is credited with constructing the first telescope to use mirrors: a [[reflecting telescope]] in [[1616]]. In 1668, [[Isaac Newton]] designed an improved a reflecting telescope that bares his name, the "[[Newtonian telescope|Newtonian reflector]]." |
The history of the telescope dates back to the Middle Ages, when [[Ibn al-Haytham]], [[Robert Grosseteste]] and other scientists studied magnifying properties of lenses. Although there were some recorded instances of pre-17th century [[Middle East|Middle-Eastern]] and [[Europe]]an opticians including [[Leonard Digges]], [[Taqi al-Din]] and others creating devices that could have functioned as telescopes, the earliest known working telescopes in the modern sense were the [[refracting telescope]]s that appeared in the [[Netherlands]] in [[1608]]. 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. [[Galileo Galilei|Galileo]] greatly improved upon this design the following year. [[Niccolò Zucchi]] is credited with constructing the first telescope to use mirrors: a [[reflecting telescope]] in [[1616]]. In 1668, [[Isaac Newton]] designed an improved a reflecting telescope that bares his name, the "[[Newtonian telescope|Newtonian reflector]]." |
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The invention of the [[achromatic lens]] in 1733, in part, corrected color aberrations present in the simple lense and enabled the construction of shorter, higher functioning refracting telescopes. Reflecting telescopes (although 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 |
The invention of the [[achromatic lens]] in 1733, in part, corrected color aberrations present in the simple lense and enabled the construction of shorter, higher functioning refracting telescopes. Reflecting telescopes (although 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.<ref>[http://www.madehow.com/inventorbios/39/Jean-Bernard-L-on-Foucault.html madehow.com - Inventor Biographies - Jean-Bernard-Léon Foucault Biography (1819-1868)]</ref>, and aluminized mirrors in 1932<ref>[http://www.cambridge.org/uk/astronomy/features/amateur/files/p28-4.pdf Bakich sample pages Chapter 2, Page 3 ''"John Donavan Strong, a young |
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physicist at the California Institute of Technology, was one |
physicist at the California Institute of Technology, was one |
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of the first to coat a mirror with aluminum. He did it by thermal vacuum evaporation. The first mirror he aluminized, in 1932, is the earliest known example of a telescope mirror |
of the first to coat a mirror with aluminum. He did it by thermal vacuum evaporation. The first mirror he aluminized, in 1932, is the earliest known example of a telescope mirror |
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coated by this technique."'']</ref> At around 1 meter (40 inches), the maximum physical size limit of the refracting telescope objectives has dictated that the vast majority of large optical researching telescopes built since the turn of the [[20th century]] be reflector-implemented. |
coated by this technique."'']</ref>. At around 1 meter (40 inches), the maximum physical size limit of the refracting telescope objectives has dictated that the vast majority of large optical researching telescopes built since the turn of the [[20th century]] be reflector-implemented. |
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The 20th century also saw the development of telescopes that worked in a wide range of wavelengths from [[radio telescope|radio]], to [[gamma-ray telescope|gamma-rays]]. 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 telescope|radio]], to [[gamma-ray telescope|gamma-rays]]. The first [[radio telescope]] went into operation in [[1937]]. Since then, a tremendous variety of complex astronomical instruments have been developed. |
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Revision as of 05:21, 31 July 2008
A telescope is an instrument designed for the observation of remote objects and the collection of electromagnetic radiation. The first modern telescopes were invented in the [[Netherlands] at the beginning of the 17th century. The name "Telescope" (from the Greek tele = 'far' and skopein = 'to look or see'; teleskopos = 'far-seeing') was invented by an unidentified Greek poet/theologian who was present at a banquet held in 1611 by Prince Federico Cesi[1]. It was given to a version of the instrument constructed by Galileo Galilei. "Telescopes" can refer to a whole range of instruments operating in most regions of the electromagnetic spectrum.
History
The history of the telescope dates back to the Middle Ages, when Ibn al-Haytham, Robert Grosseteste and other scientists studied magnifying properties of lenses. Although there were some recorded instances of pre-17th century Middle-Eastern and European opticians including Leonard Digges, Taqi al-Din and others creating devices that could have functioned as telescopes, the earliest known working telescopes in the modern sense were the refracting telescopes that appeared in the Netherlands in 1608. 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. Galileo greatly improved upon this design the following year. Niccolò Zucchi is credited with constructing the first telescope to use mirrors: a reflecting telescope in 1616. In 1668, Isaac Newton designed an improved a reflecting telescope that bares his name, the "Newtonian reflector."
The invention of the achromatic lens in 1733, in part, corrected color aberrations present in the simple lense and enabled the construction of shorter, higher functioning refracting telescopes. Reflecting telescopes (although 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.[2], and aluminized mirrors in 1932[3]. At around 1 meter (40 inches), the maximum physical size limit of the refracting telescope objectives has dictated that the vast majority of large optical researching telescopes built since the turn of the 20th century be reflector-implemented.
The 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio, to gamma-rays. The first radio telescope went into operation in 1937. Since then, a tremendous variety of complex astronomical instruments have been developed.
Types of telescopes
 | This article needs additional citations for verification. (July 2008) |
The name "telescope" covers a wide range of instruments and is difficult to define. They all have the attribute of collecting electromagnetic radiation so it can be studied or analyzed in some manner. The most common type is the optical telescope; other types also exist and are listed below.
Optical telescopes
An optical telescope gathers and focuses light mainly from the visible part of the Electromagnetic spectrum (although some work in the infrared and ultraviolet). Optical telescopes increase the apparent angular size of distant objects as well as their apparent brightness. 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 focus. Optical telescopes are used for astronomy and in many non-astronomical instruments, including: theodolites (including transits), spotting scopes, monoculars, binoculars, camera lenses, and spyglasses. There are three main types:
- The refracting telescope which uses lenses to form an image.
- The reflecting telescope which uses an arrangement of mirrors to form an image.
- The catadioptric telescope which uses mirrors combined with lenses, in front of the mirror or somewhere within the optical path, to form an image.
Radio telescopes
Radio telescopes are directional radio antennas that often have a parabolic shape. The dishes are sometimes constructed of a conductive wire mesh whose openings are smaller than the wavelength being observed. 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: see aperture synthesis. As of 2005, the current record array size is many times the width of the Earth—utilizing space-based Very Long Baseline Interferometry (VLBI) telescopes such as the Japanese HALCA (Highly Advanced Laboratory for Communications and Astronomy) VSOP (VLBI Space Observatory Program) satellite. Aperture synthesis is now also being applied to optical telescopes using optical interferometers (arrays of optical telescopes) and Aperture Masking Interferometry at single reflecting telescopes. Radio telescopes are also used to collect microwave radiation often used to help study the leftover Big Bang radiation, which can also be used to collect radiation when any visible light is obstructed or faint, such as from quasars. Some radio telescopes are used by programs such as SETI and the Arecibo Observatory to search for exterrestrial life. (see also: Wow! Signal)
X-ray and gamma-ray telescopes
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. 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.
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.
Other types
Notable telescopes
- Anglo-Australian Telescope
- Arecibo Observatory
- Atacama Large Millimeter Array
- Chandra X-ray Observatory
- CHARA (Center for High Angular Resolution Astronomy) array
- Giant Metrewave Radio Telescope
- Great Paris Exhibition Telescope of 1900
- Hale telescope 1948, 200" reflector, Mount Palomar
- Hexapod-Telescope
- Hooker Telescope 1917, 100" reflector, Mount Wilson
- Hubble Space Telescope
- IceCube Neutrino Detector
- Isaac Newton Telescope
- Keck telescope
- Leviathan of Parsonstown 1849, 79" reflector, Birr, Ireland
- Lick Observatory
- LIGO
- Lovell Telescope
- McMath-Pierce Solar Telescope
- McMath-Hulbert Observatory (Solar)
- Magdalena Ridge Observatory
- Multiple-Mirror telescope
- Navy Prototype Optical Interferometer
- Overwhelmingly Large Telescope (proposed)
- Parkes Observatory
- Southern African Large Telescope
- Subaru Telescope
- UK Schmidt Telescope
- Very Large Array
- Very Large Telescope
- Westerbork Synthesis Radio Telescope
- William Herschel Telescope
- XMM-Newton
- Yerkes 1897, 40" largest optical refractor
 | This list is incomplete; you can help by adding missing items. |
See also
- Timeline of telescope technology
- History of telescopes
- Amateur telescope making
- Angular resolution
- Aperture synthesis
- ASCOM open standards for computer control of telescopes
- BOOTES
- Depth of field
- Dynameter
- Eyepiece
- First light
- f-number
- Keyhole problem
- List of largest optical reflecting telescopes
- List of largest optical refracting telescopes
- Microscope
- Nimrud lens
- Remote Telescope Markup Language
- Robotic telescope
- Space observatory
Notes
- ^ omni-optical.com "A Very Short History of the Telescope"
- ^ madehow.com - Inventor Biographies - Jean-Bernard-Léon Foucault Biography (1819-1868)
- ^ [http://www.cambridge.org/uk/astronomy/features/amateur/files/p28-4.pdf Bakich sample pages Chapter 2, Page 3 "John Donavan Strong, a young physicist at the California Institute of Technology, was one of the first to coat a mirror with aluminum. He did it by thermal vacuum evaporation. The first mirror he aluminized, in 1932, is the earliest known example of a telescope mirror coated by this technique."]
References
- Contemporary Astronomy - Second Edition, Jay M. Pasachoff, Saunders Colleges Publishing - 1981, ISBN 0-03-057861-2
- Sabra, A. I. & Hogendijk, J. P. (2003), The Enterprise of Science in Islam: New Perspectives, MIT Press, pp. 85-118, ISBN 0262194821
External links
- "The First Telescopes". Part of an exhibit from Cosmic Journey: A History of Scientific Cosmology by the American Institute of Physics
- ESO 100 m telescope
- The Resolution of a Telescope
- Southern African Large Telescope (SALT)
- The Digges telescope of the 1570s
- The Swedish Solar telescope
- History of Refracting Telescope