acropolis5... for distance, you could probably work something with a series of smaller diameter holes, at a repeatable distance from your eyes... brim of your hat + card held between ring and little finger.... and reference the width of a man's shoulders (19")to calibrate distance... my ACOG rifle sight uses this method for stadia lines... I had to go through USAF basic looking through an aperture made by curling my index and thumb... got a lot of funny looks from the guys in the Smokey the Bear hats....