A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Ed Popko
Date: 2021 Oct 1, 08:36 -0700
After rethinking this thread and having 'solved' a number of cases, I have a methodology question.
I have had good luck in using a quadratic curve fit to various before and after near noon sights. The predicted apex look quite good for initial LAN time approximations. But several examples involve Ho's taken from a moving vessel and require Motion of the Observer (MOO) corrections to the Ho's set to refine the time of LAN.
So, here is my quandary - MOO calculations involve the vessel's speed, time delta between sight time and fix time, vessel's course and if your are advancing or retarding. No problem with these, we have them.
But here is the hick-up. MOO also needs the Zn to the body. The difference between course and Zn is a value needed in finding MOO corrections. One normally does not record the body's Zn when taking near noon shots. Perhaps a compass bearing corrected to give true would do it? Perhaps there is another simplification here that I missed.
So, for those who solved the examples in this thread, how did you handle MOO computations and refine your Ho's set for a closer approximation to LAN?