A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Bill Noyce
Date: 2016 Dec 16, 08:19 -0800
> That explains what went on in your spreadsheet, but I'd still like to know why the USNO Celestial Navigation Data site seems to always add semi-diameter. Can anyone out there explain this?
Under "Notes on the Data" (on the page with the data entry blanks), one note says:
The altitude correction values strictly apply only in the
case where the observations were in fact made from
the assumed position, and, for solar system objects,
the lower limb of the object was observed.
-- Bill N