A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Francis Upchurch
Date: 2017 Sep 5, 09:13 -0700
I've always got the correct answer without adjusting everything for "simultaneous" altitudes.
See attached, which I think explains the principles. Main quote from this:
The development of the direct fix given above is robust and exact for observations taken from the same place. The observations need not be simultaneous (although they might be with observers side by side, or with a double sextant, but their times must be registered accurately so that the GPS of the bodies at the times of their altitude measurement can be found in the almanac. The observations need not even be taken on the same day. Typically, two sights could be 1 or 2 min apart on two different bodies. The two sights could also be on one body, such as the sun...
Hope this helps. Apologies if I have this wrong, but it seems to work for me.