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A 50mm right-angle finderscope mounted on a 150mm telescope. Tour guide points out the double Finderscope on the 24.5 inch Cassegrain Telescope at the Goldendale Observatory State Park . A finderscope is an accessory sighting device used in astronomy and stargazing , typically a small auxiliary refracting telescope / monocular mounted ...
Star trail image of the north polar region. A digital camera with a standard lens is mounted on the telescope and pointed at the celestial pole. Exposure is set at "B" (Bulb) and an image is taken while the camera is slowly turned around the polar axis. [7] This yields a kind of star-trail image.
Mark III free gun reflector sight mk 9 variant. Another type of optical sight is the reflector (or "reflex") sight, a generally non-magnifying optical device that allows the user to look through a glass element and see a reflection of an illuminated aiming point or some other image superimposed on the field of view. [7]
A large German equatorial mount on the Forststernwarte Jena 50cm Cassegrain reflector telescope.. An equatorial mount is a mount for instruments that compensates for Earth's rotation by having one rotational axis, called polar axis, parallel to the Earth's axis of rotation.
Lens hoods are more prominent in long focus lenses because they have a smaller viewing angle than that of wide-angle lenses. For wide angle lenses, the length of the hood (away from the end of the lens) cannot be as long as those for telephoto lenses, as a longer hood would enter the wider field of view of the lens. [5]
The scope base is the attachment interface on the rifle's receiver, onto which the scope rings or scope mount are fixed. Early telescopic sights almost all have the rings that are fastened directly into tapped screw holes on the receiver, hence having no additional scope base other than the receiver top itself.
The centrally located sub-reflector serves to focus radio frequency signals in a similar fashion to optical telescopes. An example of a cassegrain radio antenna is the 70-meter dish at JPL's Goldstone antenna complex. For this antenna, the final focus is in front of the primary, at the top of the pedestal protruding from the mirror.
A diagram of a typical nautical sextant, a tool used in celestial navigation to measure the angle between two objects viewed by means of its optical sight. Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the ...