If you intend to spruce up your rifle with a telescopic sight for the first time, you should be knowledgeable enough about the basic parts and functions of scopes. Likewise, your understanding of scopes’ parameters and optical phenomena would play an important role in helping you choose the right scope for your rifle. Armed with the basic knowledge on scope, you can readily make a set of criteria which you can readily use as your basis in choosing a scope. If you know these basic parameters, along with the set of criteria, you can easily compare best rifle scopes that are now available in the gun market.
Parts of a Telescopic Sight
A typical telescopic sight is basically made of a scope tube, an objective assembly, a picture reversal assembly, an ocular assembly, and elevation adjustment assemblies.
- Scope Tube – The tube is the primary part of the scope that holds all the other parts in place. This is commonly seen as a pipe with a flaring at one end, or at times, at both ends, or even without the end flares at all. Scope tubes are originally made of brass or steel. However, these metals are heavy and can make the rifle unbalanced and cumbersome. The introduction of lightweight metal alloys in scope tube’s construction has remedied the problem of weight.
- Objective Assembly – This assembly is basically found at the forward end of the scope and contains the primary part of the scope—the objective lens. This is commonly seen as a flaring at one end of the scope’s tube which is almost similar to a bell, and thus, sometimes it is referred to as the “bell.” The large diameter of the objective lens provides the scope with its light gathering capability.
- Picture Reversal Assembly – The name of the assembly speaks for itself. As light passes through the primary or objective lens, light is bended and reversed producing an inverted view. This part of the scope rectifies this phenomenon.
- Ocular Assembly – This is the rearmost part of the scope that includes the ocular lens or eyepiece. The eyepiece transmits the light to the human eye for processing as imagery in the human brain.
- Elevation Adjustment Turrets – This assembly is commonly seen near the middle of the scope’s tubing and consists of a series of knobs and optional covers. The knob on top adjusts the view of the vertical plane. The other knob commonly found on the right-hand side of the scope is for adjusting the image of the horizontal plane.
Vignetting and Parallax
Vignetting and parallax are optical phenomena brought about by passing light that are to be viewed through a series of lenses like in a telescope, binoculars, and telescopic sights. Vignetting is the partial blockade of the light path that translates into the darkening of the view in the reticle. This happens when the eye is out of alignment with the exit pupil.
Parallax is an optical phenomenon that usually happens when the light that passes through the objective lens is not coincident with the reticle. Parallax can be readily identified by placing your eyes at different points behind the ocular assembly. If the crosshair in the reticle appears to be jumping all over the target, there is a parallax distortion. Some scopes incorporate parallax adjustments into their design.