RE: Binocular Question
I stand corrected as to the desired exit pupil size for low light conditions. Here's some of the info I tried to recall from memory:
<font color=maroon>The diameter, in millimeters, of the beam of light that leaves the eyepiece of a pair of binoculars is the "exit pupil". The larger the exit pupil, the brighter the image obtained will be. Having a large exit pupil is advantageous under low light conditions and at night. For astronomical applications, the exit pupil of the binocular should correspond with the amount of dilation of your eye's pupil after it has adapted to the dark. This number will be between 5mm and 9mm. 9mm of dilation is the maximum amount for the human eye, and this number tends to decrease with age.
To calculate the exit pupil, divide the size of the objective lens by the magnification of the binocular. For example, the exit pupil of 7x42 binoculars is 42 ÷ 7 = 6mm.
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