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Field flattener a correcting lens used to reduce field curvature in refracting telescopes for astrophotography. Barlow lens: Optical element to increase the telescope's focal length and magnification, narrow the field of view and reduce coma distortion, providing opposite effects of a telecompressor.
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 .
In modern optical telescopes and telescopic sights with a dual-focal plane design, the objective image is typically already inverted upon reaching the relay lenses, and thus needed to be inverted again back into an erect image (i.e. "erecting" the image) before passing to the eyepiece, so the viewer actually sees an upright target.
Galilean type Soviet-made miniature 2.5 × 17.5 monocular Diagram of a monocular using a Schmidt-Pechan prism: 1 – Objective lens 2 – Schmidt-Pechan prism 3 – Eyepiece. A monocular is a compact refracting telescope used to magnify images of distant objects, typically using an optical prism to ensure an erect image, instead of using relay lenses like most telescopic sights.
Optical telescopes can be classified by three primary optical designs (refractor, reflector, or catadioptric), by sub-designs of these types, by how they are constructed, or by the task they perform. They all have their different advantages and disadvantages and they are used in different areas of professional and amateur astronomy .
The telescope is more a discovery of optical craftsmen than an invention of a scientist. [1] [2] The lens and the properties of refracting and reflecting light had been known since antiquity, and theory on how they worked was developed by ancient Greek philosophers, preserved and expanded on in the medieval Islamic world, and had reached a significantly advanced state by the time of the ...
A refraction ray traveling through transparent material works similarly, with the addition that a refractive ray could be entering or exiting a material. Turner Whitted extended the mathematical logic for rays passing through a transparent solid to include the effects of refraction. [19] A shadow ray is traced toward each light.
The first of these was the Hamiltonian telescope patented by W. F. Hamilton in 1814. The Schupmann medial telescope designed by German optician Ludwig Schupmann near the end of the 19th century placed the catadioptric mirror beyond the focus of the refractor primary and added a third correcting/focusing lens to the system.