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Ramsden eyepiece
noun
, Optics.
- an eyepiece consisting of two plano-convex crown-glass lenses of equal focal length, placed with the convex sides facing each other and with a separation between the lenses of about two-thirds of the focal length of each.
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Word History and Origins
Origin of Ramsden eyepiece1
1840–50; named after Jesse Ramsden (1735–1800), English maker of astronomical instruments
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Example Sentences
In the Ramsden eyepiece two plano-convex lenses are also used, but they are of equal focal length, are placed at a distance apart equal to two thirds of the focal length of either, and have their convex sides facing one another.
From Project Gutenberg
The equivalent focal length of a positive or Ramsden eyepiece is equal to three fourths of the focal length of either of the lenses.
From Project Gutenberg
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