noun
: an eyepiece or adapter containing a right-angle prism or a plane mirror to reflect the rays from an object near the zenith to the side of a refracting telescope for more convenient observation — called also diagonal eyepiece
noun
: an eyepiece or adapter containing a right-angle prism or a plane mirror to reflect the rays from an object near the zenith to the side of a refracting telescope for more convenient observation — called also diagonal eyepiece
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012