▁expensive ▁and ▁heav ier ▁than ▁similarly ▁specified ▁non - st abil ised ▁bin oc ular s . ▁ ▁Al ignment ▁▁ ▁The ▁two ▁teles cop es ▁in ▁bin oc ular s ▁are ▁aligned ▁in ▁parallel ▁( col lim ated ), ▁to ▁produce ▁a ▁single ▁circular , ▁apparently ▁three - dimensional , ▁image . ▁Mis align ment ▁will ▁cause ▁the ▁bin oc ular s ▁to ▁produce ▁a ▁double ▁image . ▁Even ▁slight ▁mis align ment ▁will ▁cause ▁vague ▁dis com fort ▁and ▁visual ▁fat igue ▁as ▁the ▁brain ▁tries ▁to ▁combine ▁the ▁ske wed ▁images . ▁ ▁Al ignment ▁is ▁performed ▁by ▁small ▁movements ▁to ▁the ▁pr isms , ▁by ▁adjust ing ▁an ▁internal ▁support ▁cell ▁or ▁by ▁turning ▁external ▁set ▁sc rew s , ▁or ▁by ▁adjust ing ▁the ▁position ▁of ▁the ▁objective ▁via ▁ecc ent ric ▁rings ▁built ▁into ▁the ▁objective ▁cell . ▁Al ignment ▁is ▁usually ▁done ▁by ▁a ▁professional , ▁ ▁although ▁the ▁extern ally ▁mounted ▁adjust ment ▁features ▁can ▁be ▁accessed ▁by ▁the ▁end ▁user . ▁ ▁Opt ical ▁coat ings ▁▁ ▁Because ▁a ▁typical ▁bin oc ular ▁has ▁ 6 ▁to ▁ 1 0 ▁optical ▁elements ▁ ▁with ▁special ▁characteristics ▁and ▁up ▁to ▁ 1 6 ▁air - to - glass ▁surfaces , ▁bin oc ular ▁manufact ur ers ▁use ▁different ▁types ▁of ▁optical ▁coat ings ▁for ▁technical ▁reasons ▁and ▁to ▁improve ▁the ▁image ▁they ▁produce . ▁ ▁Anti - reflect ive ▁coat ings ▁ ▁Anti - reflect ive ▁coat ings ▁reduce ▁light ▁lost ▁at ▁every ▁optical ▁surface