A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Low Altitude Sun Artificial Horizon Exercise
From: Bill Ritchie
Date: 2020 Dec 4, 23:21 +0000
Thanks for adding the benign Florida temperature and pressure information. That makes my median result 245°/0.7nm Away.
This example highlights the fact that, at very low altitudes, variations from 'standard' T & P have a much larger effect. For example, Table A4 Zone K gives a correction of +1.5' at 1° 30' apparent altitude, but only +0.3' at 10° apparent altitude.
To change the subject slightly, why are 'standard' MSL conditions 10°C and 1010 hPa when both the International Standard Atmosphere and the US Standard Atmosphere use 15°C and 1013.25hPa? I agree it feels colder at sea and that multiples of 10 makes for an easier to use Nautical Almanac table, but
does anyone know
the real reason?
50N 003W 6°C 980 hPa.
Thanks! I'm using a different set of correction tables to you, and with the additional info I'm now up at 1° 06.2', which is just over 1/2 mile off your result. That's plenty good enough for me:) (My second ever attempt at a sight reduction, btw).
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