OK, after sending back my previous order (same product but defective monocular) I was so anxious to give it a try & hoping this monocular wud help me find the correct distance,,,well, not exactly. You wud need a very steady hand(s),,, by the way I have a perfectly steady hands but I was still shaking like heck. Dunno why. It's really hard to tell the correct distance. I think I'm going to return it .