Changes

==Etymology==

==Etymology==

New Latin telescopium, from [[Greek]] tēleskopos  farseeing, from tēle- tele- + skopos watcher; akin to Greek skopein to look  

New Latin telescopium, from [[Greek]] tēleskopos  farseeing, from tēle- tele- + skopos watcher; akin to Greek skopein to look  

*Date: [http://www.wikipedia.org/wiki/17th_Century 1648]

*Date: [https://www.wikipedia.org/wiki/17th_Century 1648]

==Definitions==

==Definitions==

*1 : a usually tubular [[optical]] instrument for viewing distant objects by means of the [[refraction]] of [[light]] rays through a [[lens]] or the [[reflection]] of [[light]] [[rays]] by a concave [[mirror]]  

*1 : a usually tubular [[optical]] instrument for viewing distant objects by means of the [[refraction]] of [[light]] rays through a [[lens]] or the [[reflection]] of [[light]] [[rays]] by a concave [[mirror]]  

A '''telescope''' is an instrument [[designed]] for the [[observation]] of remote objects by the collection of electromagnetic radiation. The first known [[practically]] functioning telescopes were [[invented]] in the Netherlands at the beginning of the 17th century. "Telescopes" can refer to a whole range of instruments operating in most regions of the [[electromagnetic]] [[spectrum]].

A '''telescope''' is an instrument [[designed]] for the [[observation]] of remote objects by the collection of electromagnetic radiation. The first known [[practically]] functioning telescopes were [[invented]] in the Netherlands at the beginning of the 17th century. "Telescopes" can refer to a whole range of instruments operating in most regions of the [[electromagnetic]] [[spectrum]].

The word "telescope" (from the [[Greek]] τῆλε, tele "far" and σκοπεῖν, skopein "to look or see"; τηλεσκόπος, teleskopos "far-seeing") was coined in 1611 by the [[Greek]] [[mathematician]] [http://en.wikipedia.org/wiki/Giovanni_Demisiani Giovanni Demisiani] for one of [http://en.wikipedia.org/wiki/Galileo_Galilei Galileo Galilei]'s instruments presented at a banquet at the [http://en.wikipedia.org/wiki/Accademia_dei_Lincei Accademia dei Lincei]. In the Starry Messenger Galileo had used the term "perspicillum".

The word "telescope" (from the [[Greek]] τῆλε, tele "far" and σκοπεῖν, skopein "to look or see"; τηλεσκόπος, teleskopos "far-seeing") was coined in 1611 by the [[Greek]] [[mathematician]] [https://en.wikipedia.org/wiki/Giovanni_Demisiani Giovanni Demisiani] for one of [https://en.wikipedia.org/wiki/Galileo_Galilei Galileo Galilei]'s instruments presented at a banquet at the [https://en.wikipedia.org/wiki/Accademia_dei_Lincei Accademia dei Lincei]. In the Starry Messenger Galileo had used the term "perspicillum".

==History==

==History==

The earliest [[evidence]] of working telescopes were the [http://en.wikipedia.org/wiki/Refracting_telescope refracting telescopes] that appeared in the Netherlands in 1608. Their [[development]] is credited to three [[individuals]]: [http://en.wikipedia.org/wiki/Hans_Lippershey Hans Lippershey] and [http://en.wikipedia.org/wiki/Zacharias_Janssen Zacharias Janssen], who were spectacle makers in Middelburg, and [http://en.wikipedia.org/wiki/Jacob_Metius Jacob Metius] of Alkmaar. Galileo greatly improved upon these [[designs]] the following year.

The earliest [[evidence]] of working telescopes were the [https://en.wikipedia.org/wiki/Refracting_telescope refracting telescopes] that appeared in the Netherlands in 1608. Their [[development]] is credited to three [[individuals]]: [https://en.wikipedia.org/wiki/Hans_Lippershey Hans Lippershey] and [https://en.wikipedia.org/wiki/Zacharias_Janssen Zacharias Janssen], who were spectacle makers in Middelburg, and [https://en.wikipedia.org/wiki/Jacob_Metius Jacob Metius] of Alkmaar. Galileo greatly improved upon these [[designs]] the following year.

The [[idea]] that a [[mirror]] could be used as an objective instead of a [[lens]] was being [[investigated]] soon after the [[invention]] of the [http://en.wikipedia.org/wiki/Refracting_telescope refracting telescope]. The [[potential]] advantages of using [http://en.wikipedia.org/wiki/Parabolic_reflector parabolic mirrors], primarily reduction of [http://en.wikipedia.org/wiki/Spherical_aberration spherical aberration] with no [http://en.wikipedia.org/wiki/Chromatic_aberration chromatic aberration], led to many proposed [[designs]] and several attempts to build [http://en.wikipedia.org/wiki/Reflecting_telescope reflecting telescopes]. In 1668, [http://en.wikipedia.org/wiki/Isaac_Newton Isaac Newton] built the first [[practical]] reflecting telescope, which bears his name, the [http://en.wikipedia.org/wiki/Newtonian_telescope Newtonian reflector].

The [[idea]] that a [[mirror]] could be used as an objective instead of a [[lens]] was being [[investigated]] soon after the [[invention]] of the [https://en.wikipedia.org/wiki/Refracting_telescope refracting telescope]. The [[potential]] advantages of using [https://en.wikipedia.org/wiki/Parabolic_reflector parabolic mirrors], primarily reduction of [https://en.wikipedia.org/wiki/Spherical_aberration spherical aberration] with no [https://en.wikipedia.org/wiki/Chromatic_aberration chromatic aberration], led to many proposed [[designs]] and several attempts to build [https://en.wikipedia.org/wiki/Reflecting_telescope reflecting telescopes]. In 1668, [https://en.wikipedia.org/wiki/Isaac_Newton Isaac Newton] built the first [[practical]] reflecting telescope, which bears his name, the [https://en.wikipedia.org/wiki/Newtonian_telescope Newtonian reflector].

The [[invention]] of the [http://en.wikipedia.org/wiki/Achromatic_lens achromatic lens] in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter, more functional refracting telescopes. [http://en.wikipedia.org/wiki/Reflecting_telescope Reflecting telescopes], though not [[limited]] by the [[color]] [[problems]] seen in refractors, were hampered by the use of fast tarnishing [http://en.wikipedia.org/wiki/Speculum_metal speculum metal] [[mirrors]] employed during the 18th and early 19th century—a problem alleviated by the introduction of silver coated glass mirrors in 1857,[7] and aluminized mirrors in 1932. The maximum physical size limit for refracting telescopes is about 1 meter (40 inches), dictating that the vast [[majority]] of large optical [[research]]ing telescopes built since the turn of the 20th century have been reflectors. The largest reflecting telescopes currently have objectives larger than 10 m (33 feet).

The [[invention]] of the [https://en.wikipedia.org/wiki/Achromatic_lens achromatic lens] in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter, more functional refracting telescopes. [https://en.wikipedia.org/wiki/Reflecting_telescope Reflecting telescopes], though not [[limited]] by the [[color]] [[problems]] seen in refractors, were hampered by the use of fast tarnishing [https://en.wikipedia.org/wiki/Speculum_metal speculum metal] [[mirrors]] employed during the 18th and early 19th century—a problem alleviated by the introduction of silver coated glass mirrors in 1857,[7] and aluminized mirrors in 1932. The maximum physical size limit for refracting telescopes is about 1 meter (40 inches), dictating that the vast [[majority]] of large optical [[research]]ing telescopes built since the turn of the 20th century have been reflectors. The largest reflecting telescopes currently have objectives larger than 10 m (33 feet).

The 20th century also saw the [[development]] of telescopes that worked in a wide range of wavelengths from [http://en.wikipedia.org/wiki/Radio_telescope radio] to [http://en.wikipedia.org/wiki/Gamma-ray_telescope gamma-rays]. The first [[purpose]] built radio telescope went into operation in 1937. Since then, a tremendous variety of [[complex]] astronomical instruments have been [[developed]].[http://en.wikipedia.org/wiki/Telescope]

The 20th century also saw the [[development]] of telescopes that worked in a wide range of wavelengths from [https://en.wikipedia.org/wiki/Radio_telescope radio] to [https://en.wikipedia.org/wiki/Gamma-ray_telescope gamma-rays]. The first [[purpose]] built radio telescope went into operation in 1937. Since then, a tremendous variety of [[complex]] astronomical instruments have been [[developed]].[https://en.wikipedia.org/wiki/Telescope]

==External links==

==External links==

* [http://galileo.rice.edu/sci/instruments/telescope.html ''The Galileo Project - The Telescope'' by Al Van Helden '']

* [https://galileo.rice.edu/sci/instruments/telescope.html ''The Galileo Project - The Telescope'' by Al Van Helden '']

* [http://www.aip.org/history/cosmology/tools/tools-first-telescopes.htm "The First Telescopes". Part of an exhibit from Cosmic Journey: A History of Scientific Cosmology] by the American Institute of Physics

* [https://www.aip.org/history/cosmology/tools/tools-first-telescopes.htm "The First Telescopes". Part of an exhibit from Cosmic Journey: A History of Scientific Cosmology] by the American Institute of Physics

* [http://www.timeline-help.com/telescope-timeline.html Timeline of telescopic technology]

* [https://www.timeline-help.com/telescope-timeline.html Timeline of telescopic technology]

[[Category: Astronomy]]

[[Category: Astronomy]]