Reticle
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A reticle, or reticule
There are many variations of reticle pattern; this article concerns itself mainly with the most rudimentary reticle: the crosshair. Crosshairs are typically represented as a pair of
Uses
Firearms
Telescopic sights for firearms, generally just called scopes, are probably the device most often associated with crosshairs.
Reticle shape
While the traditional thin crossing lines are the original and still the most familiar cross-hair shape, they are really best suited for precision aiming at high contrast targets, as the thin lines are easily lost in complex backgrounds, such as those encountered while hunting. Thicker bars are much easier to discern against a complex background, but lack the precision of thin bars. The most popular types of cross-hair in modern scopes are variants on the duplex cross-hair, with bars that are thick on the perimeter and thin out in the middle. The thick bars allow the eye to quickly locate the center of the reticle, and the thin lines in the center allow for precision aiming. The thin bars in a duplex reticle may also be designed to be used as a measure. Called a 30/30 reticle, the thin bars on such a reticle span 30 minutes of arc (0.5º), which is approximately equal to 30 inches (76 cm) at 100 yards (91 m). 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.
Wire crosshairs
![](http://upload.wikimedia.org/wikipedia/commons/thumb/4/4f/Findot_reticle.svg/220px-Findot_reticle.svg.png)
Originally crosshairs were constructed out of hair or spiderweb, these materials being sufficiently thin and strong. Many modern scopes use wire crosshairs, which can be flattened to various degrees to change the width. These wires are usually silver in color, but appear black when backlit by the image passing through the scope's optics. Wire reticles are by nature fairly simple, as they require lines that pass all the way across the reticle, and the shapes are limited to the variations in thickness allowed by flattening the wire; duplex crosshairs, and crosshairs with dots are possible, and multiple horizontal or vertical lines may be used. The advantage of wire crosshairs is that they are fairly tough and durable, and provide no obstruction to light passing through the scope.
Etched reticles
The first suggestion for etched glass reticles was made by
Illuminated reticles
Reticles may be illuminated, either by a plastic or
Graticule
A graticule is another term for reticle, frequently encountered in British and British military technical manuals, and came into common use during World War I.[7]
Reticle focal plane
The reticle may be located at the front or rear focal plane (First Focal Plane (FFP) or Second Focal Plane (SFP))[8] of the telescopic sight. 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.
Collimated reticles
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Reflector_reflex_sight_diagram_3.png/220px-Reflector_reflex_sight_diagram_3.png)
Collimated reticles are produced by non-magnifying optical devices such as
Holographic reticles
Surveying and astronomy
In older instruments, reticle crosshairs and stadia marks were made using threads taken from the cocoon of the brown recluse spider. This very fine, strong spider silk makes for an excellent crosshair.[10][11]
Surveying
In surveying, reticles are designed for specific uses.
Astronomy
For astronomical uses, reticles could be simple crosshair designs or more elaborate designs for special purposes. Telescopes used for polar alignment could have a reticle that indicates the position of Polaris relative to the north celestial pole. Telescopes that are used for very precise measurements would have a filar micrometer as a reticle; this could be adjusted by the operator to measure angular distances between stars.
For aiming telescopes,
The constellation Reticulum was designated to recognize the reticle and its contributions to astronomy.
See also
- Adrien Auzout
- Deflection (ballistics)
- Focusing screen – used in photography, and often etched
- Iron sight
- List of astronomical instruments
- Photomask – partial plate with holes or transparencies used in photolithography integrated circuit fabrication is also called a "reticle"
- Sniper
- Target blip
- Parallax
References
- ^ A Christopher Gorse, David Johnston, Martin Pritchard, Dictionary of Construction, Surveying and Civil Engineering (2 ed.), Oxford University Press, 2020 – reticule
- ^ dictionary.com – reticule
- ^ McIntyre, Thomas (2007). The Field & Stream Hunting Optics Handbook. Globe Pequot. p. 118.
- ^ Sellers, David. "Serendipity and a Spider William Gascoigne (c.1612-44) and the Invention of the Telescope Micrometer". magavelda. Retrieved 4 November 2019.
- ISBN 978-0-7134-0727-3
- ^ Richard Feynman, the red books
- ^ Glazebrook, Sir Richard, A Dictionary of Applied Physics, Macmillan and Co., London, 1923.
- ^ "First vs Second Focal Plane – What is the Differences?". 25 July 2022.
- ^ "Holographic Sights for SOCOM M4s". Retrieved 30 August 2012.
- ^ Raymond Davis, Francis Foote, Joe Kelly, Surveying, Theory and Practice, McGraw-Hill Book Company, 1966 LC 64-66263
- ^ Berenbaum, May R., Field Notes - Spin Control, The Sciences, The New York Academy Of Sciences, September/October 1995
External links
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