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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.
A reticle, or reticule [1] [2] also known as a graticule, is a pattern of fine lines or markings built into the eyepiece of an optical device such as a telescopic sight, spotting scope, theodolite, optical microscope or the screen of an oscilloscope, to provide measurement references during visual inspections.
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 focusing screen is a flat translucent material, either a ground glass or Fresnel lens, found in a system camera that allows the user of the camera to preview the framed image in a viewfinder. Often, focusing screens are available in variants with different etched markings for various purposes. [ 1 ]
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.
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]
[1] [2] These sights work on the simple optical principle that anything at the focus of a lens or curved mirror (such as an illuminated reticle) will appear to be sitting in front of the viewer at infinity. Reflector sights employ some form of "reflector" to allow the viewer to see the infinity image and the field of view at the same time ...