NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Extremely poor conditions??
From: Alexandre Eremenko
Date: 2012 Mar 21, 13:24 -0400
From: Alexandre Eremenko
Date: 2012 Mar 21, 13:24 -0400
David, > 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. No. The first statement does not imply the second. Just look at the Almanac table for the dip. The reason is that the ray from the Sun travels through the whole atmosphere (so it has plenty of time to get distorted by 30') But the ray from the horizon travels to our eye only few miles. So this second ray is distorted much less. As the dip table in the Almanac shows. Alex.
