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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Biruni and the radius of the Earth by dip
From: John Huth
Date: 2011 Jan 5, 10:27 -0500
From: John Huth
Date: 2011 Jan 5, 10:27 -0500
Maybe I am misunderstanding. Let me look at the formula again - on that website you had, there was a crude figure of merit for what I thought was refraction that was 1.75 moa * sqrt(h) where h is in meters. It seemed to be for refraction and it gives 40 moa if I plug into it.
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Keeping up with the grind
Where did you get 6 moa from?
On Wed, Jan 5, 2011 at 10:17 AM, Marcel Tschudin <marcel.e.tschudin@gmail.com> wrote:
John, you wrote:> peak, ....
> Both the dip and the refraction are in the 40 arc minute region for a 500 m
Could there be a misunderstanding? From a 500m high peak the horizon
has a geometrical dip (without refraction) of about 40 moa. The
refraction increases this geometrical dip by e.g. 6 moa leading to an
observed dip of e.g. 46 moa. In this case we deal with the
"terrestrial" refraction which is considerably smaller than the
"astronomical" refraction since in the "terrestrial" case the length
of the ray path through the atmosphere is much shorter.
Marcel
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Keeping up with the grind
