Telescopes

15 August Telescopes The telescope was invented in the year 1608. It works with the help of two lenses. It has an objective lens in the front which serves the function of generating an upside-down image of the thing that is being viewed through the telescope. Another lens, called as the eye lens is closer to the eye. Its function is to magnify the upside-down image produced by the objective lens. Lenses with spherical surfaces have certain aberrations or limitations. Thus, either kind of lens may have several lenses when it is to be used in a telescope because this helps overcome limitations. Some astronomical telescopes make use of a large mirror instead of the objective lens. Both eye lens and field lens are present in the eye piece of the telescope. Optical telescopes contain multiple lenses which gather light from the distant objects. The light is focused by reflecting or by bending. Optical telescopes come in two designs, namely the reflector telescopes and the refracting telescopes.
The Hubble Space Telescope, named after Edwin P. Hubble who invented it in 1929 is one of the telescopes invented in the last 100 years that work on the same principles as those of the earliest telescopes (Hubblesite). Solar cells power up this telescope. It has a large concave mirror known as the Cassegrain configuration that has a hole. The main mirror in the back reflects the incident light rays which are later again reflected by a little mirror to a focus behind the main mirror.
Works Cited:
Hubblesite. “ Hubble Essentials: About Edwin Hubble.” n. d. Web. 15 Aug. 2011.
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