thewood1 -> RE: Periscope (1/30/2022 12:58:27 AM)
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"The following requirements are for periscopes which have been used in submarines: field, at least 40 degrees to 45 degrees; magnification, between 1.2x and 1.5x; exit pupil, at least 5 millimeters in diameter; length, not specified; external diameter, 5 inches; thickness of walls, about 1/4 inch. Let us find possible periscope lengths under these conditions for the two magnifications given, 1.2x and 1.5x. The inside diameter of the tube is 5 inches minus 1/2 inch, or 4 1/2 inches. The lens, lens-holding ring, supporting tube, and so forth take up another 1/2 inch of diameter, leaving about 4 inches free for the objective." https://maritime.org/doc/fleetsub/pscope/chap1.htm#1A
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