NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Refraction at the horizon.
From: Bill Noyce
Date: 2008 Mar 15, 15:10 -0400
From: Bill Noyce
Date: 2008 Mar 15, 15:10 -0400
George Huxtable wrote, concerning timing sunsets:
> But on second thoughts, does that matter a jot?. No, it isn't a coastal
> site, it's an ocean site, as far as sunset timings are concerned. Those are
> only affected by what's going on in the atmosphere, further out than that
> distant horizon. Atmospheric effects, between that horizon point and the
> observation point, have no effect at all, inversions or not, because they
> bend light from the Sun upper-limb and light from the horizon in EXACTLY the
> same way. If I've got that right, the only relevant temperature profiles
> would be those taken from 50 to say 150 miles out to sea. If Marcel knows of
> such information, it could be of interest."
I think the refraction between the observer and his horizon *does*
make a bit of difference in how sunsets are timed. Specifically, it
affects how distant that horizon actually is, and therefore affects
the direction of the light-ray that just grazes the ocean surface.
How big is this effect?
-- Bill N
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