Scopes Glossary

Whether you are looking for your first riflescope, or you're on old-time hunter, it's important to be familiar with the terms related to scopes. These terms will help you to understand riflescopes and other scopes more and to be more comfortable discussing them and looking for the right items for your scope.

Adjustable Objective

This is a tool on the scope that allows you to adjust your scope's parallax to your desired distance. It is usually either a dial that is near the objective end of the scope or a knob on the left hand side of the turret housing. You are able to move these adjustments as you desire to create a more clear picture.

Airgun Scope

Spring piston airguns have a more harsh recoil than do regular rifles. Therefore, an airgun scope is made to handle that dual-recoil present in the airgun scope. Were you to use a regular non-airgun rated scope with your airgun, you would quickly find the the scope would be destroyed by the airgun recoil. In addition to their durability and strength, airgun scopes have adjustable objectives, allowing the user to benefit from a higher magnification at shorter distances.


Scopes have microscopic coatings on their lenses to reduce glare that comes from reflection. The more coating there is, the better the light transmission is. Good coatings are quite expensive, and it's important to know what type of coating, and what glass you have on your scope. Here are important terms for coating.

Coated: This is one layer that is on at least one lens surface.

Fully Coated: This is when there is one layer on all air to glass surfaces.

Multicoated: This is when there are multiple layers on at least one lens surface.

Fully Multicoated: This is when there are multiple layers on all air to glass surfaces.

Exit Pupil

This is a small circle or column of light that you can see in the ocular lens when your scope is held at arm's length. A larger exit pupil means a brighter image entering your eye.

Eye Relief

This is the distance that your eye needs to be from the ocular lens for you to still get a full field of view.

Field of View

Often written as FOV, the field of view is the amount of area that you can see through your scope at 100 yards. The FOV is inversely proportioned to the magnification. The greater the magnification, the less the FOV will be, and the less the magnification, the larger the FOV will be.

Kentucky Windage

This is the amount of change that you make to your point of aim, without adjusting the scope, to adjust to the wind effects on your projectile.


This is the amount that the scope magnifies the objectives that you are looking at through the lens. It is indicated by the symbol "x" and makes objects appear to be that much closer than they would appear with the naked eye. If your scope is a 5x, then it makes objects appear five times closer than you can see them with your eye.


This is the front end of the barrel and the place where the projectile exits.

Objective Lens

This is the lens that is closest to the object you are looking at. The larger the objective lens, the more light enters the scope. It is measured in millimeters in diameter.

Ocular Lens

This is the lens that is closest to your eye.


This is the lines, dots or crosshairs that are in the scope that are superimposed on your target and help you to aim your scope at the target.


This is a knob on the outside center part of the scope tube. It helps you to adjust the elevation and windage to take these items into account as they influence your point of impact.

Twilight Factor

This is the measurement that allows you to evaluate how productive your scope will be in low light conditions. The higher the twilight factor is, the better able you'll be to use the scope during low light and twilight conditions. The formula for this factor is the square root of the magnification multiplied by the diameter of the objective lines. Keep in mind that the coating and the glass quality are not factored into this figure.


This is the distance that you are sighting your target. If you've adjusted your scope to sight in at 100 yards, then you have a 100 yard zero.

These terms should help you to understand scopes more and to be ready to start to use your scope for better, more accurate hunting.