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On Nov 19, 2004, at 11:50 AM, Trevor J. Kenchington wrote:

> Alex asked:
>
>> Does our "day vision" have higher resolution than
>> the "night vision"?
>
> Yes...
>
>
>  Whether
> or not it would be possible to use a sextant while looking out of the
> corner of your eye, I cannot say.
>

For stars, I believe one needs to learn to flick one's eye across the
subject.  It's difficult to describe; you're not so much looking out of
the corner of your eye as not looking out the center of your eye.  This
is based on experience with microscopes and jeweler's loupes, not
sextants, so may be inaccurate!

I have not had a huge amount of experience with star-to-star distances,
but, on occasion I was reasonably precise (and accurate).  It does
appear to be a skill that is more difficult to learn than measurements
of the sun.

Part of the problem for me is that I cannot resolve star coincidences
to better than about 1' of accuracy: once the images overlap, if I
rotate the micrometer by 0.5' to 1.0' they still appear to be
overlapped.  So I resort to turning the micrometer at a steady rate and
trying to dead-center the coincidence by assessing the rate of
convergence.  Here, it may be that rocking the micrometer on either
side of coincidence would allow greater accuracy than always turning
the micrometer in one direction, given a micrometer with minimal
backlash.

Fred

   

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