NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Fleming
Date: 2012 Mar 21, 08:10 -0700
The errors in the observed altitues imply observations were smaller than predicted.
We know that sun observed with LL touching horizon horizon is actually just below horizon. That is the sun LL is seen 30 min higher in sky than it is. This means that usual conditions also raise the apparent horizon by the same 30 mins or the visible horizon is further than the geometric horizon.
The atmosphere is the cause of this refraction, the more air the more bending.
Normal surface temperatures bend terrestial rays 30 min. A colder surface air layer would be denser, oep, and would therfore haise the horizon further producing smaller than expected altitudes.
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