The term "scope" for a rifle comes from the word telescope. As such, a scope makes distance objects appear closer through the eyepiece. Rifle scopes have aiming points that are called reticules. Different scopes have different types of reticules. The most commonly known reticule, or aiming point, for a scope is the traditional crosshairs. The aiming point for scopes that have crosshairs is where the two lines, one horizontal and one vertical, intersect. At the extended magnification ranges of some scopes, parallax error can cause the reticule to shift. The adjustable objective rifle scope corrects this parallax error.
Items you will need
Rifle
Ammunition
Prepare for shooting your rifle in the same manner as if your rifle scope were not adjustable. This includes adhering to the standard safety practices of using firearms, whether you are target shooting or hunting.
Aim at the target. The adjustable objective rifle scope comes into play at long distance, generally greater than 100 yards or meters. See if an adjustment needs to be made by checking for parallax error. If you move your eye across the eyepiece slightly left and right, the reticule should remain on target. If the reticule shifts and is no longer on target as your eye moves, the objective lens of the scope needs adjustment.
Turn the adjustment for the objective lens on the scope until the reticule remains on target even as you shift your eye back and forth across the eyepiece. The adjustment can be a rotating ring at the barrel end of the scope or a turret knob on the side of the scope.
Focus the scope again on the target. The adjustment for the objective lens will correct for parallax error, but it can cause the target to get out of focus. By focusing again, you'll have a clearer shot at the target.
Take a steady breath and take your shot. Congratulations. You've just shot a rifle with an adjustable objective rifle scope.