NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Very Small Altitude-Accurate Results
From: Stan K
Date: 2015 Aug 11, 20:38 -0400
From: Stan K
Date: 2015 Aug 11, 20:38 -0400
Related to this subject, it should be noted that the Nautical Almanac changed its refraction corrections in 2004. Apparently an oversight, the refraction formula on page 280 did not change until 2005. The difference is only significant for altitudes less than 2º, but the change affected the critical values of apparent altitude on the Altitude Correction Table 10º-90º - Sun, Stars, Planets (Table A2).
The new formula on page 280 does not always agree with the new Table A2, as the old formula did not always agree with the old Table A2. If they changed the critical values of feet to make it agree, it would not agree with the critical values of meters, and vice versa. But, practically speaking, either formula is close enough. Other factors come into play in "real life" anyway, such as anomalous refraction.
Stan
