19:00 Feb 28, 2011 |
English to Romanian translations [PRO] Science - Astronomy & Space / Space | |||||||
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| Selected response from: Sandra & Kenneth Grossman Israel Local time: 11:19 | ||||||
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3 +1 | fraza |
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Adfaptive Optics - explicatii si poze |
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phrase fraza Explanation: La observatorul Keck se utilizeaza iluminare laser pt. a contracara/corecta/elimina efectele turbulentei atm. terestre. -------------------------------------------------- Note added at 32 mins (2011-02-28 19:33:46 GMT) -------------------------------------------------- Vezi explicatiile. Poze a doua metode de iluminare laser in acest scop - la situl indicat. |
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Reference: Adfaptive Optics - explicatii si poze Reference information: Turbulence in the Earth's atmosphere limits the performance of ground-based astronomical telescopes. In addition to making a star twinkle, turbulence spreads out the light from a star so that it appears as a fuzzy blob when viewed through a telescope. This blurring effect is so strong that even the largest ground-based telescopes, the two 10-m Keck Telescopes in Hawaii, have no better spatial resolution than a modest 8-inch backyard telescope! One of the major motivations for launching telescopes into space is to overcome this blurring due to the Earth's atmosphere, so that images will have higher spatial resolution than has been possible to date from the ground. How adaptive optics works. Adaptive optics technology can correct for the blurring caused by the Earth's atmosphere, and can make Earth-bound telescopes "see" almost as clearly as if they were in space. Assume that you wish to observe a faint galaxy. The first step is to find a relatively bright star close to the galaxy. a) Light from both this "guide star" and the galaxy passes through the telescope's optics. The star's light is sent to a special high-speed camera, called a "wavefront sensor," that can measure hundreds of times a second how the star's light is distorted by the turbulence. b) This information is sent to a fast computer, which calculates the shape to apply to a special "deformable mirror" (usually placed behind the main mirror of the telescope). This mirror cancels out the distortions due to turbulence. c) Light from both the "guide star" and the galaxy is reflected off the deformable mirror. Both are now sharpened because the distortions due to turbulence have been removed. The concept of "laser guide stars" was suggested in the early 1980's in both the military and astronomical communities. A laser beam is mounted on the telescope and pointed at the object to be observed. One concept is shown in the Figure on the left below. In this "sodium laser guide star" concept, the laser light is tuned to a yellow color (similar to the color of low-pressure sodium street lights) that excites a layer of sodium atoms about 60 miles up in the atmosphere. The sodium atoms glow in a small spot on the sky, making an "artificial star" that can be used to measure atmospheric turbulence. http://www.ucolick.org/~max/max-web/History_AO_Max.htm -------------------------------------------------- Note added at 25 mins (2011-02-28 19:26:14 GMT) -------------------------------------------------- "Adaptive" - of course. |
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