A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Gary LaPook
Date: 2021 Apr 15, 22:37 -0700
The only time I ever used a sun compass idea was on a flight from Dublin to Chicago. I arranged to be in a window seat on the left side of the aircraft so that I could take sun observations with my A-7 bubble sextant. This is the best kind of sextant to use since the eyepiece can be rotated so that it is convenient to hold the instrument in front of you while your are actually sighting out the window, 90 degrees to your side.
I was working the sights with my Bygrave replica and I needed to apply the corriolis correction. To do this I needed the relative bearing to the sun since the correction varies with the sin of the relative bearing. Simple. I had a standard protractor and I put the flat base of it against the window (I assumed that the window surface was parallel to the longitude axis of the plane.) I dangled my pencil over the pivot point on the protractor and observed where its shodow cut the arc and used that measurement for the coriolis correction. Z= .0262 X groundspeed (knots) X sin of latitude X sin of relative bearing. I assumed the normal cruising speed of jets of 450 knots.