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George-
 Latitude about 43N and tht puts a late afternoon sun around 11-12d above
the horizon.
 I am aware of the possible errors, causes, and effects and did in fact run
them all through a calculator to see just how far a change of 5F or 50mb or
eye height would affect things, I have notes on exactly how far each can
affect the readings.
 And I am aware of sextant index error which I think was the root
problem--the index zero wheel may have loosened under my gloved hand, I will
be checking this again and have since re-zero'd on a star which gives me a
far tighter zero.
 The effect of taking a warm sextant out of the car does not exist, after an
hour in my trunk near 35F the sextant is nicely prechilled thank you.

 The question remains: Has anyone found that it is harder to get absolute
accuracy when shooting an afternoon sun from a lattitude 43N during the
winter, when refraction causes the three factors of eye height, air
temperature, and air pressue to be far greater in effect than they are for a
typical summer sight from these same lattitudes?

 I also suspect that some mirage (from the ocean/air temperature difference)
and a rough horizon (either thermal mirage or waves at sea) were involved. I
wasn't getting a real crisp sight and I've gotten crisper before, I'm
wondering if that air/water temp difference causes enough distrotion in the
winter to make it something to routinely be mindful of.

   

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