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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Meridian Transit of the Sun and Daily Pages
From: Paul Hirose
Date: 2015 Oct 12, 16:42 -0700
From: Paul Hirose
Date: 2015 Oct 12, 16:42 -0700
On 2015-10-11 13:37, Stan K wrote: > For example, for 0h UT on 1 January 2015, the values of GHA of the Sun are given for several sources: > USNO web site 179º12.2' > Nautical Almanac 179º12.0' > Reed Navigation 179º12.1' > sun.xls 179º12.1' > Navigator Lite 179º12.2' > Nautical Almanac (Ruiz) 179º12.2' > Celestial Tools (Accurate) 179º12.2' > Celestial Tools (NA) 179º12.0' > > > Other sources have values of 179º12.22', 179º12.17', 179º12.169' (which all round to 179º12.2'), 179º12.2', and 179º12.1'. Rounded to 0.1', 11 of the 14 sources I checked say 179º12.2'. According to the results below, a trifling decrease of about 1.1″ in GHA would make a program round down rather than up to the nearest .1′. That may explain some of the discrepancies noted by Stan. My sexagesimal angles were converted from decimal values at full accuracy, not the rounded values in the left column. That's why the first two lines have identical decimals but different sexagesimals. 179.20280° (179°12′10.08″) USNO MICA 2.2.2 179.20280° (179°12′10.09″) JPL HORIZONS [1] 179.20281° (179°12′10.12″) SofaJpl 2.0 demo program [1] 179.20281° (179°12′10.12″) Tinyac [1] [1] Program is capable of greater precision but I did not request it.
