{HEAD ~ The main optical housing} 56 includes a viewing aperture 68 serving as an entrance pupil region to enable {TAIL ~ light} from the object being viewed to pass into the reflecting assemblies of the optical system 
{ HEAD ~ The main optical housing } 56 includes a viewing aperture 68 serving as an entrance pupil region to enable { TAIL ~ light } from the object being viewed to pass into the reflecting assemblies of the optical system
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH