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A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope). The refracting telescope design was originally used in spyglasses and astronomical telescopes but is also used for long-focus camera lenses.
The Swedish 1-m Solar Telescope, with a lens diameter of 43 inches, is technically the largest, with 39 inches clear for the aperture.The second largest refracting telescope in the world is the Yerkes Observatory 40 inch (102 cm) refractor, used for astronomical and scientific observation for over a century.
An Achromatic telescope uses an achromatic lens to correct for this. An achromatic lens is a compound lenses made with two types of glass with different dispersion . One element, a concave lens made out of Flint glass , has relatively high dispersion, while the other, a convex element made of Crown glass , has a lower dispersion.
Past product lines include refractors up to 206mm in aperture, a catadioptric design of 254mm, and an astrograph of 305mm. As of the end of 2021, the company's line of telescopes (optical tubes only, consisting of objective lens, tube, and focuser) included only a 92mm refractor and a 130mm refractor, priced in the $4000–$7000 range.
Alvan Clark & Sons made the 36-inch (910 mm) objective lens for the Lick Observatory refractor, shown here in an 1889 drawing. The telescope was designed and built by the Warner & Swasey Company Alvan Clark & Sons was an American maker of optics that became famous for crafting lenses for some of the largest refracting telescopes of the 19th and ...
The list includes various refractors and reflectors that were active at some time between about 1799 to 1901. The main material used early on for reflecting telescope mirrors was speculum metal , which reflected only about two-thirds of the incident light, and which tarnished , requiring maintenance.
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