NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: sextant index error measurement
From: Frank Reed CT
Date: 2006 Nov 3, 22:55 EST
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From: Frank Reed CT
Date: 2006 Nov 3, 22:55 EST
Peter, you wrote:
"The experiment you are working you way towards carrying out involves
observations made over a distance parallel to the ground, close to the ground.
Refraction will depend on your atmospheric conditions there, and could be
different to the refractive effect from sighting from eye height
skywards."
That's called terrestrial refraction. Although it is variable, it is
typically 0.1 minutes of arc per nautical mile and only rarely more than 0.5
minutes of arc per n.m. Even if they decide to run this test over a range of 500
feet, the refraction will be negligible. This refraction would apply to BOTH
beams similarly, of course, and so the difference in refraction would be smaller
still. In short, refraction is completely negligible for this test.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
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