T3D Re: hawk eyes

[bercov@xxxxxxxxxxx (John Bercovitz)]

> The hawk buteo has 1,000,000 photoreceptors per square mm, compared to 
> about 200,000 per square mm in the human eye.

Now that's interesting.  People can see about 1 moa and their receptors
are about 1/2 moa on center.  I think 1/2 moa is around a 3 micron spacing.
1/(200000^0.5) = 2 microns.  (Jim C will be back tomorrow to tell us which.)  
The hawk's receptors must then be 3 microns / 5^0.5 = 1+ microns on center
or 1/(1000000^0.5) = 1 microns.  Either way, the hawk's receptors are
getting down to a couple of wavelengths on center.  I suppose there's not
much of a gap between receptors.  8-)

John B


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