Teach Astronomy - Reflecting Telescopes

refractor telescopes video

	Teach Astronomy - Reflecting Telescopes www.teachastronomy.com Essentially all modern telescopes used by research astronomers are reflecting telescopes. They use mirrors to bend, deflect, and focus light to form an image. The first reflecting telescope was perfected by Isaac Newton, and reflecting telescopes of larger and larger aperture have been produced ever since. Edwin Hubble discovered the distant nature of galaxies and the expansion of the universe using the largest reflecting telescope at the time just outside Los Angeles. For several decades the largest reflector was the 200-inch or 5-meter diameter telescope at Mount Palomar. The Russians built a 6-meter telescope in the 1970s. Currently the largest single mirror telescopes are just over 8-meters in diameter. The advantage of a reflecting telescope relative to a refractor is that the mirror can be very large and thin because the light is only reflected from the front surface. A reflector also reflects all the waves of light by equal amounts, and so the images that are formed have no chromatic aberration. The two slight disadvantages of reflecting telescopes are that the mirror's surface is exposed to the elements and must be occasionally recoated and the fact that since the light is focused in front of the mirror, some of the light must be blocked by a secondary or by a detector to gather the light.	From: astropedia Views: 30 0 ratings
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