so I bought a hammers adjustable objective 3-9x32 scope. never owned one before and have done a bunch of reading from different internet sources but still have questions. first is why optically center the crosshairs when I'm gonna have to move them to zero the scope for the yardage I want to zero? I'm on paper and very close with plenty of adjustment both directions. after mounting the scope I set my objective to infinity setting and then looked into the blue sky to set my rectile focus so it was sharp and clear. now I can turn the scope power down to lets say 5 then look at my target which is only 3/4'' dot @20 yrd's then turn my objective lens till its clear which does not correspond with the factory marked yardages printed on the end. no worries as I've read there never right anyways just a ballpark figure. I've also read the rectile focus once set should never be touched again unless there is say a prescription change etc . now if I were to go higher or lower with the magnification power 3-9 then the scope gets blurry. so my question is do I just use the objective lens adjustment to keep my scope clear and focused. if someone had a accurate scope set up link pertaining to proper set up of a ao scope I would like to see it. seems there are lots opinions as to the correct way but all are different.