Next message: Bill: "Re: Sumner's Line (Navigation question)"
Gary wrote
"Capt. Sumner had to work the time sight twice, doing the math two times
which was difficult in the days before inspection tables and computers.
Marc De St. Hilaire's contribution ...People should
consider using this new (old) method today."
Yes, the old becomes new again. In her book "Practical Celestial
Navigation" Susan Howell notes a calculator method of determining two points
to establish and LOP. She attribute it to the USNO Circular #155, Almanac
for Computers, 1977, 1 October 1976.
Longitude = GHA Body +/- cos^-1 (sin Ho - (Sin L sin d)) / (cos L cos d)
which uses GHA instead of using time and Eqn of time.
Bill
