Last month, I began a series on rifle sights as an introduction to which sights might best suit your rifle’s purpose. The first article covered iron sights. This post continues the subject, focusing now on telescopic sights. Telescopic sights, commonly referred to as “scopes,” use a system of lenses to magnify the appearance of a target from a distance. Not surprisingly, this magnification effect on the user’s field of vision is beneficial for styles of shooting that require precision from a distance. While distance shots, to some degree, are capable with mere iron sights, adding a scope reduces some of the challenge involved.
How They Work
Telescopic sights generally have a combination of curved lenses and reflective surfaces within metal sleeve. The shooter looks through the ocular lens (smaller, and of lower magnification), and the objective lens at the scope’s far end increases magnification. Some telescopic sights are fixed in the amount of magnification they can provide. Others are variable. The “power” of the magnification of any particular scope is usually denoted like so: optical magnification x obejctive lens diameter (for fixed magnification optics), or minimum magnification – maximum magnification x objective lens diameter. For example, the Leupold scope shown below is denoted 2-12×42. Which means the lowest magnification is 2x larger than naked eye, minimum, with a maximum of 12x, and the objective lens is 42mm in diameter (lenses are often measured in metrics, rather than the US customary units).
Having a larger objective lens diameter is a benefit as well as a disadvantage. The larger the objective lens, the more light can enter through the end of the telescopic sight. More light provides a brighter image. However, having a large optic means the profile is larger. If one wishes to put their rifle through heavy use, the delicate glass within their optic may not survive potential impacts. And, the more glass on the scope’s end, the more surface there is to try to keep clean and free from scratches – both of which could impede vision through the implement temporarily or permanently. However, if one is gentle enough with their scope use and storage, these issues can be avoided.
Another notable feature of telescopic sights which could contribute to whether or not they suit your rifle’s purpose is the visual phenomenon of field of vision that is necessarily altered. The magnification that telescopic sights provide is limited to the expanse of the lens. Therefore, an additional benefit to having a scope with a wide objective lens allows for a larger field of view when looking down the scope. When one is shooting from a fixed vantage, or other position that requires little movement, having a limited field of view is not as significant of a detriment as to those who may wish to change shooting location frequently in one sitting, or for someone who wishes to shoot while on the move.
There is a vast range of telescopic sights available, not only with varying levels of magnification and lens diameter, but also differing coatings for the glass (both to protect the glass itself, and to alter the way the light enters the optic, which could improve clarity and color, levels of adjustment for windage and elevation, and there are even some scopes that include electronic elements that assist in ballistics calculations. There is also a wide array of reticles of varying sight pictures and materials (many are made of thin wire located on the first focal plane within the scope, while others are etched glass plates fixed in the same location).
If shooting from a fixed position with a need for precise shots aimed at a distant target, the quality of the telescopic optics one uses could be as important, if not more important, than the rifle upon which the scope is mounted. However, if your rifle is better suited to close quarter combat, or short range target engagements, a reflector or reflex sight may be a better bet for your shooting experience. The next article in this series will introduce the benefits and downsides of that style of optics, so stay tuned for Part 3.