How about 782mm f/2.2?

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DiffractionLtd Regular Member • Posts: 326
How about 782mm f/2.2?

The lens is a mirror, of course, with 14" wide optics. You mount a conventional camera, DSLR, mirrorless right in front (facing backward relative to the lens)where it intercepts the light cone from the main mirror that the secondary mirror normally would. The primary mirror has an f/2.0 focal ratio. Correction of aberrations is handled by a front lens known as a corrector plate. The lens is 42 inches long, 16 inches in diameter and weights 75lbs. The lens supports a 60mm wide aberration-free image plane.

Technically, it's a telescope but could be used for long-distance low-light surveillance, atmospheric conditions permitting.

https://www.youtube.com/watch?v=ikSPdasfEwA

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