By levelling the rifle and scope and using a plum line to fine tune scope reticle! Also using a bright flashlight Shawn through the objective works great as well. I had two of them mounted on a FX crown and my Air arms s510
I have had two Aztec ffp both returned! reticle not Square or plum with scope tube. Couldn’t even come close to levelling the scope with the rifle. I replaced it with the hawk 4 x 16 sidewinder first focal plane in my opinion a way better scope then the Aztec
