Reticle

Today, engraved lines or embedded fibers may be replaced by a digital image superimposed on a screen or eyepiece.

Both terms may be used to describe any set of patterns used for aiding visual measurements and calibrations, but in modern use reticle is most commonly used for weapon sights, while graticule is more widely used for non-weapon measuring instruments such as oscilloscope display, astronomic telescopes, microscopes and slides, surveying instruments and other similar devices.

Crosshairs are typically represented as a pair of perpendicularly intersecting lines in the shape of a cross, "+", though many variations of additional features exist including dots, posts, concentric circles/horseshoes, chevrons, graduated markings, or a combination of above.

This enables an experienced shooter to deduce, on the basis of the known size of an object in view, (as opposed to guess or estimate) the range within an acceptable error limit.

The advantage of wire crosshairs is that they are fairly tough and durable, and provide no obstruction to light passing through the scope.

Red is the most common color used, as it is the least destructive to the shooter's night vision, but some products use green or yellow illumination, either as a single colour or changeable via user selection.

On fixed power telescopic sights there is no significant difference, but on variable power telescopic sights the front plane reticle remains at a constant size compared to the target, while rear plane reticles remain a constant size to the user as the target image grows and shrinks.

Front focal plane reticles are slightly more durable, but most American users prefer that the reticle remains constant as the image changes size, so nearly all modern American variable power telescopic sights are rear focal plane designs.

[citation needed] American and European high end optics manufacturers often leave the customer the choice between a FFP or SFP mounted reticle.

The use of a hologram also eliminates the need for image dimming narrow band reflective coatings and allows for reticles of almost any shape or mil size.

In older instruments, reticle crosshairs and stadia marks were made using threads taken from the cocoon of the brown recluse spider.