Refractors

Where light is concerned, the word refract means “to bend.” A refracting telescope (usually called a refractor) does this with a carefully made lens system. If the surfaces of the lenses have the proper shape, the light will come to a focus. Placing an eyepiece at that “focal point” will let you see what you have pointed the telescope at. Dutch eyeglass-maker Hans Lipperhey made the first telescope (a refractor) in 1608. His patent application described “an instrument for seeing faraway things as though nearby.” The tube magnified objects about three times. Italian inventor Galileo Galilei was the first to use the telescope to study celestial objects, and what he saw revolutionized astronomy forever. Two words you’ll see when reading about today’s refractors are achromat and apochromat. Each is a lens system combining different types of glass. Achromat means “not color dependent.” Such a lens has two pieces of glass and does a pretty good job of bringing all colors of light to the same focus. Apochromatic lenses are also available. They are the top of the line, and their front lenses combine up to five pieces of glass. There are everal factors you may want to consider when you buy a telescope. First, the overall quality of refractors has risen dramatically. Second, better lenses have made shorter tubes possible. Finally, lighter materials mean small models now transport more easily. Not only does this simplify travel to your favorite viewing site, but it also helps you decide whether or not to set your scope up in the backyard for a quick view of the Moon or Jupiter.

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