Hello everyone, I'm new to scopes and I got a new one installed on my Diana 350 Magnum air rifle, the scope is 4x32. My problem is that I sighted the scope at 25 yards then 50 yards and I was hitting targets with it quite well, I tried it today at 100 and 150 yards by shooting at a pond of water (I purposely shot at water to easily find out where the pellet is hitting) and it turns out the pellet is going lower then the target. My question is, should the scope have a different vertical "tuning" for different distances? And if the answer is yes should I manually change the tuning every time I need to fire at something which is near or far? Thank you for your much appreciated help.