David, you will find that to get a excellent image on the addon, the parrelex on your scope will only need to be on low, try it first as a spotter, focus in using the barrel, no mag on the digital screen ! Then mount it to your scope, Re focus to your reticle, try it at say 50yrds first, your parrelex will either need to be on (20yrds or infinity) scope dependent! I've got 1 & use it on my airmax 4-16x50 & airmax 3-9x40 , and only need to focus the screen & centre the reticle, if swapping between scopes ! I absolutely love mine , it's the only night vision I've ever got on with,