[header] How to use adjustable objective rifle scopes [title] Be sure that your scope is mounted properly. [step] Sighting-in can have been done preliminarily, but additional sighting-in will be desirable after following these steps : [title] Know your rifle. [step] There are actually two optical systems in a rifle scope. 
The objective (front lens) focuses the target image on the reticle (cross-hairs); the eyepiece (rear lens) focuses the eye on the reticle. The eyepiece must first be adjusted before any adjustment of the objective.