eBay
Huge ! ! !

Huge mirror lens 2540mm focal length, aperture F/8 ! ! !
These lenses were used by the NASA for tracking the Saturn V or similar.
I was told by the grandson of its producer John H. Ransom, that the tragedy of  
the Space Shuttle Challenger was tracked and filmed with Jonel lenses 
( the most of them are still in use ).
They used high speed 70mm movie cameras like the Photosonics 70mm 10R with
up to 125 fps on 6x6 frames ( this camera is also for sale, seperate )
It is a Schmidt-Cassegrain design with a two element field corrector to produce a 57x57mm image format ( 80mm image diameter or more ).
This lens is unique. Optics mint, barrel mint- ( some loss of paint ).
The barrel is incorporating a system to avoid humidity inside, it is very rigid, and the design is very sophisticated, compared to modern Astro cameras.

Original cost : a family home.
180 pounds in original case. Ask me for tripod and head and for focusing units.