A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Modris Fersters
Date: 2021 Aug 1, 07:30 -0700
Hello everyone interested in lunars!
In NavList archive I found wonderful posts by Frank Reed concerning effect of the altitude accuracy of the Object (Sun, star, planet) and the Moon on cleared lunar distance (including the 90 degrees miracle). Frank worked out two formulas to determine the necessary accuracy of altitudes to provide maximum error in cleared lunar distance 0,1 minute of arc.
I just for fun made two tables in Excel (based on Frank's formulas) where it can be found the altitude errors when error in cleared lunar distance is 0,1'. Maybe it will be interesting to look at these values, because usually in books we can read something like that: "altitudes can be measured with accuracy of several arc minutes". But in fact the needed accuracy of the altitudes is dependent on lunar distance and altitude values. It is not constant value. Of course, on avarage the term "several arcminutes" will work perfectly. The altitudes and lunar distances are printed with 5 degrees step. 90 degrees miracle can be seen in Moon altitude table (when altitude of the Moon does not affect cleared distance).