▁the ▁angle ▁between ▁marks ▁equal ▁to ▁ 5   mil . ▁One ▁mil ▁is ▁equivalent ▁to ▁the ▁angle ▁between ▁the ▁top ▁and ▁bottom ▁of ▁an ▁object ▁one ▁meter ▁in ▁height ▁at ▁a ▁distance ▁of ▁ 1 0 0 0 ▁meters . ▁ ▁Therefore , ▁to ▁estimate ▁the ▁distance ▁to ▁an ▁object ▁that ▁is ▁a ▁known ▁height ▁the ▁formula ▁is : ▁ ▁where : ▁▁▁ ▁is ▁the ▁Dist ance ▁to ▁the ▁object ▁in ▁meters . ▁▁ ▁is ▁the ▁known ▁Object ▁Height . ▁▁ ▁is ▁the ▁angular ▁height ▁of ▁the ▁object ▁in ▁number ▁of ▁Mil . ▁ ▁With ▁the ▁typical ▁ 5 ▁mil ▁scale ▁( each ▁mark ▁is ▁ 5 ▁mil ), ▁a ▁l ighth ouse ▁that ▁is ▁ 3 ▁marks ▁high ▁that ▁is ▁known ▁to ▁be ▁ 1 2 0 ▁meters ▁tall ▁is ▁ 8 0 0 0 ▁meters ▁distance . ▁ ▁Military ▁▁ ▁Bin oc ular s ▁have ▁a ▁long ▁history ▁of ▁military ▁use . ▁Gal ile an ▁designs ▁were ▁widely ▁used ▁up ▁to ▁the ▁end ▁of ▁the ▁ 1 9 th ▁century ▁when ▁they ▁gave ▁way ▁to ▁por ro ▁pr ism ▁types . ▁Bin oc ular s ▁constructed ▁for ▁general ▁military ▁use ▁tend ▁to ▁be ▁more ▁rug ged ▁than ▁their ▁civil ian ▁counter parts . ▁They ▁generally ▁avoid ▁frag ile ▁center ▁focus ▁arrang ements ▁in ▁favor ▁of ▁independent ▁focus , ▁which ▁also ▁makes ▁for ▁easier , ▁more ▁effective ▁weather proof ing . ▁Pr ism ▁sets ▁in ▁military ▁bin oc ular s ▁may ▁have ▁redundant ▁al umin ized ▁coat ings ▁on ▁their ▁pr