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Old November 25, 2019, 09:00 AM   #3
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 7,513
Its Bob Jones. I, too, sometimes get him confused with Neil Jones who makes reloading dies. Shot many matches with him.

Those lenses help focus and sharpen target bullseye and front sight images in the eye. Sometimes slightly magnified so its easier to align them.

Focal lengths of those lenses is calculated by dividing 1 diopter (1 meter or about 40 inches) by the lens diopter value. A 0.50 (1/2) diopter lens has a 2 meter focal length, about 80 inches.

Last edited by Bart B.; November 25, 2019 at 09:11 AM.
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