You don't and you can't. I do notice though, if a good shooter, slammer etc., pops up out of no-where, presents himself immediately within range, relatively quickly...I can pull off the shotreal smooth,without having to think about it too much. These are always my best shots........On the other hand when a large buck gets within eyesight, slightly out of range, and makes you watch him for 15 min., it's enough to give a man a coronary. You know, the one that will stare in your direction, not allowing you even blink your eyes, then slowly walking within range (meanwhile your staring at a set of antlers that only have been seen in your dreams...until now). By the time he gets to you, your heart isbeating so hard that it'smoving simultaniously with your lighted pin![&o].[:'(]..........Ithink everyone has a little buck fever in them.