NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Refraction
From: Marcel Tschudin
Date: 2005 Aug 4, 19:20 +0300
From: Marcel Tschudin
Date: 2005 Aug 4, 19:20 +0300
Fred, Yes, how do I get in this? Just trying to cover in a self-made program the situation from an object at the horizon (over sea level) as seen from a mountain or air craft. The "real" calculation is done via integration. But since this is not very practical one uses approximative formulae like e.g. the one from Bennett which Meeus mentions in his book Astronomical Algorithms. All tables on refraction I found so far do end at 0? elevation and for none of the approximative formulae I could find an indication that they also would be valid for negative elevations. I also was wandering whether the approximate formulae could be used by calculating the Refraction R for e.g. -2? the follwing way: R(-2?) = R(0?) + ( R(0?) - R(+2?) ) If this would be correct then one would not need separate formula for negative elevations. Greetings from Marcel