Vivitar 600mm f/8 Series 1 Solid Catadioptric Lens with T-Mount for Nikon F-Mount {35.5 Rear}

Vivitar 600mm f/8 Solid Catadioptric lens is a solid glass design, with no air spaces between the front lens, rear mirror and front reflector. The 600mm f/8, along with its sister the 800mm F/11, Solid Catadioptric were created for the U.S. Military by Perkin-Elmer. 

The 600mm f/8 Solid Catadioptric lens is an extremely compact telephoto lens. Its optical element is comprised of refractive glass and silver coated mirrors. This design closely forms a solid single element making it virtually shock-proof and removes the hot-spot found in many lenses. It weighs 3lbs and longer than 3 inches long. It has a rugged design with a metal lens barrel. The lens employs 4° angle of view, 23ft close focusing distance, 35.5mm filter thread and stops down to the equivalent f/16 with Neutral Density FilterThe lens is extremely short compared to the effective focal length of 800mm.