see also:

• super telephoto mirror lenses

• this super telephoto lens introduced in ? is a modified Maksutov catadioptric mirror lens, and as with all such mirror lenses, share the following characteristics:
  • manual focus
  • fixed aperture (in this case f/10)
  • virtual elimination of chromatic aberration as uses mirror rather than lenses
    • also means focus position for infrared photography is the same as for light photography
  • central mirror:
    • allows much more compact lens length as the optic path is reflected internally twice
    • by necessity, blocks some of the light and thus causes:
      • decrease in image contrast
      • characteristic “doughnut” shaped bokeh imagery in out of focus areas
• the Rubinar 1000mm f/10 is a later version of this lens

• 1000mm focal length and field of view (2.5°) at infinity focus
• fixed f/10 aperture
• lens elements, ? groups
• closest focus 7.3m (24')
• M116 rear filter thread
• M42 lens mount thread
• 122mm (4.8“) diameter, 250mm (9.8”) long and 1.9kg (4.2lb)

• http://www.tracyleerose.com/Txt/Tutorials/Tutorial_Lens/MTO.html
• http://www.its-network.de/content/sonderthemen/ausruestung/mto1000/maksutov1.php - German