The Complete Handbook of Scopes

Chapter 1: Understanding Scopes

A scope is a precision optical instrument designed to make distant objects appear larger and clearer, and when mounted on a rifle, to provide a reliable aiming reference that a shooter can use to place a projectile accurately at distance. The concept is simple, but the implementation is remarkably involved, and the difference between a quality scope and a cheap one is not just resolution on a test chart. It is the difference between a tool that performs consistently for years and one that fails when you need it most: when you are dialing windage on a moving target in a competition, or when you are responsible for a single shot on a hunt.

To understand a scope, you must understand the job it does. The optical fire control system of a modern rifle scope is, at its core, a small telescope with an adjustable reticle. Light enters the objective lens, passes through a series of lenses and prisms that invert and magnify the image, and lands in your eye as a right-side-up, magnified image of the world. Superimposed on that image is a reticle: crosshairs, a dot, or a more complex pattern that appears to sit at the same distance as the target and provides a reference point for aiming. The entire assembly is built with strict tolerances, because the human eye is sensitive to minute misalignments, and the system as a whole must hold its zero under the violent acceleration of a rifle recoiling.