When setting the reticle focus, you shouldn't spend a long time staring into the scope.
Aim the scope at a blank background like a white wall or the sky so you're not trying to focus on the background. Then look through the scope at the reticle. Adjust it until it looks right, then let your eyes rest for awhile and repeat the procedure until it looks right when you first look into the scope with rested eyes.
Aim the scope at a blank background like a white wall or the sky so you're not trying to focus on the background. Then look through the scope at the reticle. Adjust it until it looks right, then let your eyes rest for awhile and repeat the procedure until it looks right when you first look into the scope with rested eyes.