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