NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Riddle of the Secant
From: Don Seltzer
Date: 2026 Aug 10, 17:10 -0400
From: Don Seltzer
Date: 2026 Aug 10, 17:10 -0400
I will guess 1973, the introduction of the HP-45.
Or maybe 1974 with the TI SR-50.
Both had the cosine function, but not the secant.
Don Seltzer
On Mon, Aug 10, 2026 at 2:45 PM NavList Community <NavList@navlist.net> wrote:
Riddle of the Secant
From: Jacquelin Hardy
Date: 2026 Aug 10, 11:22 -0700As a young 2nd mate on a cargo ship, I used to take a sun amplitude and calculate the gyro error with the formula:
sin(Amplitude) = sin(declination) * secant(latitude)
And then an event happened and I stopped using the above formula and I used instead:
sin(Ampl.) = sin(declination) / cos(latitude)What is this event ?
How old am I ?
Good luck
