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On 2001-11-15 05:35, Donnie B. wrote:
I don't mean to quibble, Bob, but 0.1cm^3 seems a bit small to me, considering this would be in the dark with the iris fully dilated. But it's not a biggie.
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O (::kid-friendly mode on:
heck, let's quibble. 7mm is pretty much a maximum, and that gets harder to attain with age. If you assume 5mm, then the area is (.5)^2 times pi/4, which is .196 cm^2 (note "2").
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Also, I assume these numbers apply to the "night vision" portion of the retina, rather than the day-vision, high-resolution fovea. (I can never remember whether it's rods or cones that handle low-light situations). So to see the 6th-magnitude star, we're using averted vision, right?
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Up till now, I don't think the numbers have anything to do with rods or cones. So far, the calculations have been just how much light is actually entering the eye, not how much the receptors are excited.