This is a "Catadioptric" type telephoto lens with two silver evaporation coated reflective mirrors. The silver evaporation coating on the rear lens surface compensates for spherical aberrations on reflective surface giving high quality images throughout the focusing range. Tele-macro is also available with a short minimum focusing distance of 1.7m (67") and a maximum magnification ratio of 1:3.

Mount Adaptall II (Interchangeable mount system)

7 elements in 4 groups
Angle of View:  5°
Minimum Aperture:  8 (fixed) 
Minimum Focus:  66.9in. (1.7m)
Macro Mag. Ratio 1:3
Filter Diameter: ø30.5 (front 82)
Weight: 18.9oz. (535gm)
Diameter x Length: ø3.3 x 3.6in. (ø84 x 91.5mm)