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    Re: Atmospheric refraction high above Sea Level
    From: Antoine Couëtte
    Date: 2024 Jul 6, 10:22 -0700


    Thank you for your quite interesting and comprehensive reply, especially as regards the difference between the USNO Nautical Almanac (NAL) current Refraction tables and the pre-2004 former ones.

    I have been able to reconcile your such NAL quoted current values with this table found here : " https://www.thenauticalalmanac.com/Increments_and_Corrections/Altitude_Correction_Tables.pdf " which looks like being a copy of the official NAL current refractions Tables I had been looking for.

    The NAL current Stars Refraction Tables have become much closer to the unchanged ones of the Bureau des Longitudes Éphémerides Nautiques (EN) in particular for the standard 0° refraction now at -33.8' in both tables vs. the former 0.7' difference in the pre-2004 publications. Under 5°, the current differences between the current NAL and the EN remain under 0.3' and they gradually vanish under 0.1' from 5° and above. 

    Then, yes, the EN based "Brute Force Method" Refractions [-1° , 0°] Table (A) yields results probably as good as the ones derived in that range by the Auer-Standish numerical Integration.


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