A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Antoine Couëtte
Date: 2015 May 14, 00:10 -0700
If no error from my side, it looks that this extra-correction for Venus is a "phase correction" to account for the appreciable difference between center of mass and center of light of Venus as seen from the Earth. This correction may reach some 15" (arc seconds) for Venus under extreme cases. "Stricto sensu" it concerns all Planets, but in practice it is relevant and appreciable only for Planets inside the Earth Orbit, i.e. Mercury and Venus, with only Venus in practice.
This Correction is to be performed in a plan [very] close from the Ecliptic. Its tabular sporadic character coupled with its apparently altitude relation is only a coarse approximation. But better something rough than nothing.
Best Friendly Regards
Antoine M. "Kermit" Couëtte