NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Altitude correction using Artificial Horizon?
From: Kirk Benson
Date: 2000 Sep 05, 6:01 PM
From: Kirk Benson
Date: 2000 Sep 05, 6:01 PM
Is it necessary to apply any correction for altitude when reducing a sun sight taken with an artificial horizon? If the two sextant images are superimposed, I could presume that the sight is the center of the disc and no correction is necessary. However, the correction tables in the Nautical Almanac show that the correction is skewed between UL and LL. For example, at an apparent altitude of 20 degrees in September, the corrections are +13.5(ll)/-18.3(UL). The total difference is 31.8' which is exactly twice the SD of 15.9'. So I might argue that I should use a correction "in the middle" of -2.4'. Any clarification on this point would be appreciated. Similarly, if I take the sight by aligning the LL of the sun image with the UL of the image in the AH, should I just correct the sight by the SD? Kirk Benson 34d 10.8' N 84d 12.7' W
