NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Table A4 + elevation?
From: George Huxtable
Date: 2003 May 3, 22:08 +0100
From: George Huxtable
Date: 2003 May 3, 22:08 +0100
Marc Bernstein said- >The sight reduction tables for air navigation do have refraction tables. The >altitudes are listed in 5000' increments up to 55,000' and there is a >correction table for non-standard temperatures that goes from +47 to -95 C! > >For 2100' and 20C, a little interpolation shows you need to subtract about >1.5' from Hs I don't understand this. What is Hs, in this context? The amount of refraction from a celestial body varies VERY greatly with its angular altitude in the sky, and so does the additional correction for height-and-temperature. Marc quotes an interpolated correction of about 1.5', without specifying any angle for the incoming light. Such a large correction could only apply to a very small apparent angle, of the order of a couple of degrees, that is, a body just above the horizon, way below what any self-respecting navigator would choose to observe. Can Marc explain further, please? George. ================================================================ contact George Huxtable by email at george@huxtable.u-net.com, by phone at 01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. ================================================================
