A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Antoine Couëtte
Date: 2021 Oct 29, 12:11 -0700
Celestial Navigation Data for 2021 Oct 19 at 21:59:27 UT For Assumed Position: Latitude N 41 18.4 Longitude W 72 30.0 Almanac Data | Altitude Corrections Object GHA Dec Hc Zn | Refr SD PA Sum o ' o ' o ' o | ' ' ' 'Moon phase is waxing, 99% illuminated.
there is a definite refraction correction error for the Moon which should show -31.0' exactly like for the Sun, instead of currently showing -24.0' .
As earlier surmised, the Moon refraction Correction showing up as " -24.0 " is the Inverse Refraction - actually the right refraction function to be used in such reverse engineering - applied by error to the Geocentric Height "Hc" while it should be applied to the Topocentric unrefracted height.
from Éphémérides Nautiques
Published Refr in
As earlier surmised, this mismatch is only visible onto Low Alt Bodies with a significant HP, in other words, it is only visible for Lady Moon quite close from the Horizon.
Hence it fully explains why the example you just published shows a perfect match between the former USNO Web Application and the current USNO Web Application clone since Lady Moon height is about 25° in it.
This bug should be very simple and straightforward to correct : simply apply Inv (Ref) to Topocentric Height vs. Geocentric height.
Hope it helps !
Antoine M. "Kermit" Couëtte