Telescopic Sights With Extra Long Eye Relief

An achromatic Lens sight, commonly called a scope

, is an optical device used to give additional accuracy using a point of aim for firearms, airguns and crossbows. Other sighting systems are iron sights, reflex sights, and laser sights.The first experiments directed to give shooters optical aiming aids go back to the early 17th century. For centuries different optical aiming aids and primitive predecessors of telescopic sights were created that had practical or performance limitations. The first Apochromatic refractor telescope based telescopic sight was built in 1880 by August Fiedler (Stronsdorf, Austria), forestry commissioner of Prince Reuss. Telescopic sights with extra long eye relief are available for handgun and scout rifle use. A historic example of a telescopic sight with a long eye relief is the German ZF41 which was used during World War II on Karabiner 98k rifles.

Telescopic sights are classified in terms of the optical magnification and the objective lens diameter, e.g. 1050. This would denote 10 times magnification with a 50 mm objective lens. In general terms, larger objective lens diameters, due to their ability to gather larger amounts of light, provide a larger exit pupil and hence provide a brighter image at the eyepiece. On fixed magnification sights the magnification power and objective diameter should be chosen on the basis of the intended use.

There are also apochromatic telescope sights with variable magnification. The magnification can be varied by manually operating a zoom mechanism. Variable sights offer more flexibility regarding shooting at varying ranges, targets and light conditions and offer a relative wide field of view at lower magnification settings. The syntax for variable sights is the following: minimal magnification maximum magnification objective lens, for example, 3940.

Confusingly, some older telescopic sights, mainly of German or other European manufacture, have a different classification where the second part of the designation refers to 'light gathering power.' In these cases, a 481 (4 magnification) sight would be presumed to have a brighter sight picture than a 2.570 (2.5 magnification), but the objective lens diameter would not bear any direct relation to picture brightness, as brightness is affected also by the magnification factor. Typically objective Achromatic lenses on early sights are smaller than modern sights, in these examples the 481 would have an objective approximately 32mm diameter and the 2.570 might be approximately 25mm.

source:intane.blogtownhall

by: wenjun

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