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A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light). The first known practical telescopes were invented in the Netherlands at the beginning of the 17th century, using glass lenses. They found use in terrestrial applications and astronomy. Within a few decades, the reflecting telescope was invented, which used mirrors. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. The word ''telescope'' now refers to a wide range of instruments detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors. The word "''telescope''" (from the Ancient Greek τῆλε, ''tele'' "far" and σκοπεῖν, ''skopein'' "to look or see"; τηλεσκόπος, ''teleskopos'' "far-seeing") was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei's instruments presented at a banquet at the Accademia dei Lincei.〔( archive.org "Galileo His Life And Work" BY James La Rosa "''Galileo usually called the telescope occhicde or cannocchiale ; and now he calls the microscope occhialino. The name telescope was first suggested by Demisiani in 1612''" )〕〔Sobel (2000, p.43), Drake (1978, p.196)〕〔Rosen, Edward, ''The Naming of the Telescope'' (1947)〕 In the ''Starry Messenger'', Galileo had used the term "perspicillum". ==History== (詳細はrefracting telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals: Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, and Jacob Metius of Alkmaar.〔( galileo.rice.edu ''The Galileo Project > Science > The Telescope'' by Al Van Helden: "The Hague discussed the patent applications first of Hans Lipperhey of Middelburg, and then of Jacob Metius of Alkmaar... another citizen of Middelburg, Sacharias Janssen had a telescope at about the same time but was at the Frankfurt Fair where he tried to sell it" )〕 Galileo heard about the Dutch telescope in June 1609, built his own within a month,〔(Aleck Loker, Profiles in Colonial History, page 15 )〕 and improved upon the design in the following year. In the same year, Galileo became the first person to point a telescope skyward in order to make telescopic observations of a celestial object.〔(Telescope history )〕 The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope.〔(Stargazer – By Fred Watson, Inc. NetLibrary, Page 109 )〕 The potential advantages of using parabolic mirrors—reduction of spherical aberration and no chromatic aberration—led to many proposed designs and several attempts to build reflecting telescopes.〔Attempts by Niccolò Zucchi and James Gregory and theoretical designs by Bonaventura Cavalieri, Marin Mersenne, and Gregory among others〕 In 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name, the Newtonian reflector. The invention of the achromatic lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter, more functional refracting telescopes. 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,〔( madehow.com – Inventor Biographies – Jean-Bernard-Léon Foucault Biography (1819–1868) )〕 and aluminized mirrors in 1932.〔(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." )〕 The maximum physical size limit for refracting telescopes is about 1 meter (40 inches), dictating that the vast majority of large optical researching 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), and work is underway on several 30-40m designs. The 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「telescope」の詳細全文を読む スポンサード リンク
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