You'll get about 9000 opinions on this one dude. Some guys can do both eyes open, some guys can't. It's a matter of personal preference and also eye dominance and eyesight capabilities. For me personally, I'm blessed with great eyesight, and right eye dominant, so I can do both eyes open,and my right eye takes the lead on focusing and I shoot well like that. I can shoot with my left eye closed, but I'm steadier holding with both open.

You'll just have to try it and see what works better.

Also when aiming, focus your eyes on the target, not the pin. And I mean focus on that target. Let the pin hover, don't follow it around with your eye,stay focused on the spot you want to hit........andsqueeze the trigger. This is the biggest tip anyone can give you in regards to aiming.