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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.
It was first proposed in 1817 by the mathematician Carl Friedrich Gauss for a refracting telescope design, but was seldom implemented and is better known as the basis for the Double-Gauss lens first proposed in 1888 by Alvan Graham Clark, which is a four-element, four-group compound lens that uses a symmetric pair of Gauss lenses.
Telescopes can be classified by optical design or mechanical design/construction. Telescopes can also be classified by where they are placed, such as space telescopes . One major determining factor is type of light, or particle being observed including devices referred to as "telescopes" that do not form an image or use optics.
Chester Moore Hall (9 December 1703, Leigh, Essex, England – 17 March 1771, Sutton) was a British lawyer and inventor who produced the first achromatic lenses in 1729 or 1733 (accounts differ). He used the achromatic lens to build the first achromatic telescope, a refracting telescope free from chromatic aberration (colour distortion). [1]
The ETX started out as a 90 mm (3-1/2") Maksutov Cassegrain telescope (first produced in 1996) and took advantage of high volume mass production and simplified optical and parts construction to open a new market for a cheap alternative to the very expensive Questar 3-1/2 Maksutov Cassegrain [1] [2] The ETX "line" has been expanded to 105 mm, and 125 mm Maksutov Cassegrains and achromatic ...
An achromatic doublet brings red and blue light to the same focus, and is the earliest example of an achromatic lens. In an achromatic lens, two wavelengths are brought into the same focus, here red and blue. An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses ...
Cone of light behind an achromatic doublet objective lens (A) without (red) and with (green) a Barlow lens optical element (B). The Barlow lens, named after Peter Barlow, is a type of diverging lens which, used in series with other optics in an optical system, increases the effective focal length of an optical system as perceived by all components that are after it in the system.
The original two element Gauss was a telescope objective lens consisting of closely spaced positive and negative menisci, invented in 1817 by Carl Friedrich Gauss as an improvement to the Fraunhofer Achromatic telescope objective lens by adding a meniscus lens to its single convex and concave lens design.