Out of interest, the Pecar 4x81 had a objective lens diameter of 36mm. The 81 was the luminosity figure derived from 9 squared (9x9) therefore 4x9 = 36.
Out of interest, the Pecar 4x81 had a objective lens diameter of 36mm. The 81 was the luminosity figure derived from 9 squared (9x9) therefore 4x9 = 36.
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