From Wikipedia, the free encyclopedia For other uses, see Telescope (disambiguation). The 100 inch (2.54 m) Hooker reflecting telescope at Mount Wilson Observatory near Los Angeles, USA. 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 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 Galileis instruments presented at a banquet at the Accademia dei Lincei Copernican system, in astronomy, model of the solar system centred on the Sun, with Earth and other planets moving around it, formulated by Nicolaus Copernicus, and published in 1543. It appeared with an introduction by Rhäticus (Rheticus) as De revolutionibus orbium coelestium libri VI (“Six Books Concerning the Revolutions of the Heavenly Orbs”). The Copernican system gave a truer picture than the older Ptolemaic system, which was geocentric, or centred on Earth. It correctly described the Sun as having a central position relative to Earth and other planets. Copernicus retained from Ptolemy of Alexandria, although in somewhat altered form, the imaginary clockwork of epicycles and deferents (orbital circles upon circles), to explain the seemingly irregular movements of the planets in terms of circular motion at uniform speeds. A spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials.[1] The variable measured is most often the lights intensity but could also, for instance, be the polarization state. The independent variable is usually the wavelength of the light or a unit directly proportional to the photon energy, such as wavenumber or electron volts, which has a reciprocal relationship to wavelength. A spectrometer is used in spectroscopy for producing spectral lines and measuring their wavelengths and intensities. Spectrometer is a term that is applied to instruments that operate over a very wide range of wavelengths, from gamma rays and X-rays into the far infrared. If the instrument is designed to measure the spectrum in absolute units rather than relative units, then it is typically called a spectrophotometer. The majority of spectrophotometers are used in spectral regions near the visible spectrum.
Posted on: Thu, 08 Jan 2015 03:28:47 +0000
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