NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2016 Jan 21, 06:16 -0800
Jim,
(6.) is the prime vertical formula used with the azimuth formula (2.) when the azimuth is near 90° or 270°.
(7.) is the amplitude formula used to determine the azimuth of the Sun when the lower limb is 2/3 of a diameter above the visible horizon.
Greg Rudzinski
From: Jim Rives
Date: 2016 Jan 20, 12:58 -0800Hello,
My father-in-law, who sailed for years out of Huntington, LI, passed away a year ago. In one of his desk drawers I found a 10" Sterlin Slide Rule, No. 584. It is white plastic, not very eleborate. (however, still beyond my slide rule skills!) He had scratched the following 7 formulae on it. I am just wondering if anyone would recognize the text or method he was using this rule for:
In no particular order:
1. sin h = sin L sin d + cos L x cos d cos t
2. sin z = cos d sin t sec h
3. cos co-d = cos co-h cos co-L + sin co-h sin co-L cos z
4. sin t = (sin z sin co-h)/sin co-d
5. cos t = tan d cot L
6. sin h = sin d csc L
7 sin A = sin d sec L
