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A telescopic sight, commonly referred to as a '''scope''', is a device used to give an accurate point of aim for a Firearm . Other sighting systems are Iron Sights , Red Dot Sights , and Laser Sights . Telescopic sights are classified in terms of the Optical Magnification and the Objective Lens Diameter , e.g. 10×50. This would denote 10 times Magnification with a 50 mm objective lens. In general terms, larger objective lens diameters are better (collect more light and give a wider field of view), the magnification power should be chosen on the basis of the intended use. There are also Adjustable Objectives sights where the magnification can be changed by manually turning one part, the syntax is the following: minimal magnification – maximum magnification × objective lens, for example, 3–9×40. Telescopic sights have both advantages and disadvantages relative to iron sights. Standard doctrine with iron sights is to focus the eye on the front sight and align it with the resulting blur of the target and the rear sight; most shooters have difficulty doing this, as the eye tends to be drawn to the target, blurring both sights. Telescopic sights allow the user to focus on both the Crosshair and the target at the same time, as the lenses project the crosshair into the distance (50 to 100 yards or meters for Rimfire scopes, 150 or more for Centerfire calibers). This, combined with telescopic magnification, clarifies the target and makes the target stand out against the background. The main disadvantage of magnification is that the area to either side of the target is obscured by the tube of the sight. The higher the magnification, the narrower the field of view in the sight, and the more area that is hidden. Rapid fire target shooters use Red Dot Sight s, which have no magnification; this gives them the best field of view while maintaining the single focal plane of a telescopic sight. Telescopic sights are expensive, and require additional training to align. Sight alignment with telescopic sights is a matter of making the field of vision circular to minimize Parallax error. Until the 1990s, Military use of telescopic sights was restricted to Sniper s because of the fragility of optical components. The glass lenses are prone to breakage, and environmental conditions such as condensation, precipitation, dirt, and mud obscure external lenses. The scope tube also adds significant bulk to the rifle. Snipers generally used moderate to high magnification scopes with special reticles that allow them to estimate range to the target. Telescopic sights provide some tactical disadvantages. Snipers rely on stealth and concealment to get close to their target, and a telescopic sight can hinder this. Sunlight may reflect from the lens and a sniper raising his head to use a telescopic sight might reveal his position. The famous Finnish sniper Simo Häyhä preferred to use iron sights rather than telescopic sights to present less of a target. The Israeli military began widespread use of telescopic sights by ordinary infantrymen to increase hit probability (especially in dim light) and extend effective range of standard issue infantry rifles. Palestinian militants in the Al Aqsa Intifada likewise found that adding an inexpensive scope to an AK-47 increased its effectiveness. Today, several militaries issue telescopic sights to their Infantry , usually compact, low-magnification sights suitable for snap-shooting, like Red Dot Sight s. American GIs in Iraq frequently purchase their own and carry them from home. The British army fielded the SA80 rifle with a 4× optical sight as standard issue to allow average shooters to fire more accurately. The Canadian Forces standard C7 Rifle has a 3.7× optical sight. EXTERNAL LINKS |
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