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> Frank,
>
>> Yes. The human eye certainly has higher resolution in daylight. I think we
>> discussed this at length a couple of years ago, didn't we?
>
> Sure. But as it always happens, there was a long
> discussion with different opinions and I don't remember
> whether it came to a definite conclusion.
>
> One alternative explanation offered was that
> the eye pupil becomes larger in the darkness:-)
>
> Alex.

In the process of moving while trying to care for an aging mother hours
away, so please excuse my lack of specific detail. Frank pointed out an
excellent article in, if memory serves, Sky & Telescope a while back that
dealt with corrective surgery, night eyeglass prescriptions, and the lack of
ability to resolve a point source as the eye night adapts. Please check the
archives and/or read the article.

Unless you are a submariner trying to distinguish a horizon in the dead of
night, I feel there is a strong case to be made for keeping the pupil small.
Some list members I have met personally find an IE check with a star very
difficult.  Ironically, night myopia appears to decrease with age. Some
texts (Bauer?) recommend popping out and and doing the observation so one
does not strain the eye. Unless absolutely necessary, I try to keep the
pupil as small as possible and get better results.

I would be hard pressed to make a case for depth of field being a factor for
a target that is, for all practical purposes, at infinity.

Bill


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