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1 December 2008 15:21
- the part of a telescope (or binoculars) into which you (typically) look
- a.k.a. "ocular" or (less commonly) "ocular lens;" often abbreviated EP
- telescope eyepieces are typically removable, binocular eyepieces typically are not
- many telescopes (refractors, Newtonian reflectors) achieve focus by moving the eyepiece by means of a mechanical focuser forwards or backwards in the light cone near the focal point of the telescope's objective
- on some binoculars, both eyepieces are focusable via helical focusers, on others only one eyepiece can be adjusted (a diopter adjustment)
- common eyepiece designs include: Plössl, orthoscopic (Abbe), Kellner, and Erfle
- some eyepiece designs are patented and/or the name is trademarked, e.g., TeleVue's Radian, Panoptic, Nagler, and Ethos lines
- the focal length (FL) of the eyepiece determines the magnification of the view through a given telescope; the lower the eyepiece FL, the higher the magnification: magnification = telescope's FL / eyepiece's FL
- for better viewing positions, eyepieces are generally placed in diagonals on cadioptric and refractor telescopes
- common barrel sizes for eyepieces are 1.25 inches and 2 inches. Less common (and typically now only found on lower quality scopes) are 0.965 inch barrels.
- some eyepiece barrels have "safety cutouts" so set screws will hold them more securely; they can be a liability for people who have accessories (diagonals/focusers/visual backs) with compression rings as the cutouts sometimes "hang" on the compression rings
30 November 2008 13:33
- a telescope design utilizing both mirrors and lenses, as opposed to reflectors - which only have mirrors, and refractors, which only have lenses
- popular catadioptric designs include the Schmidt-Cassegrain (SCT), the Maksutov-Cassegrain (MCT), and the Schmidt-Newtonian (SN), among others
- catadipotric is often shortened to "cat," - an astronomer who is called a "cat fancier" most likely doesn't know a tabby from a Russian Blue, but probably owns one or more catadioptric optical instruments
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in the image below, light entering the instrument from the left passes through a lens (the Schmidt corrector), reflects off the primary mirror at the far right, back to the secondary mirror on the left, and finally out the right hand-side through the visual back to an eyepiece or camera
25 November 2008 23:26
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the (scientific) study of all aspects of celestial bodies, including their appearance, makeup and motions
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a sometimes maddening yet enjoyable hobby, undertaken by fools and masochists, that makes one painfully aware of light pollution, bad weather, and the cost of quality glass and workmanship
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(capitalized) a magazine published since August 1973 devoted to the hobby and science of astronomy
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-.com the website of the magazine Astronomy. Link: www.astronomy.com
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Orion Telescopes
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