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Re: Biruni and the radius of the Earth by dip
From: Marcel Tschudin
Date: 2011 Jan 5, 17:42 +0200
From: Marcel Tschudin
Date: 2011 Jan 5, 17:42 +0200
Uups, I only notice now that I made here a mistake: > John, you wrote: >> Both the dip and the refraction are in the 40 arc minute region for a 500 m >> peak, .... > 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 > The refraction has to be deducted from the geometrical dip. Please read therefore: "... leading to an observed dip of e.g. 34 moa. " Marcel
