A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Gary LaPook
Date: 2011 Nov 25, 23:49 -0800
Paul Hirose worked out a sample problem using the Bygrave method on a 10 inch slide rule, using latitude 34° N, dec. 20° N and LHA 14°, see:
I decided to do the same sample problem on several slide rules. I also worked it out using a calculator so I know that the correct answer for Hc = 71° 17.4'. Paul got 71° 17' a difference of 0.4'.
Using a cheep Sterling plastic slide rule the Hc = 71° 18', difference of 0.6'.
Using a K&E 4081-3 I got 71° 18', difference 0.6'.
Using a K&E 4080-3 I got 71° 17', difference 0.4'.
Using a Pickett N803-ES I got 71° 20', difference 2.6'.
Using my Bygrave cylindrical replica I got 71° 18', difference 0.6'.
Using my flat Bygrave I got 71° 18', difference 0.6'.
So using a ten inch slide rule with the Bygrave method produces quite usable results but the two Bygraves produce better consistent accuracy.
A computer simulation confirms this, see:
--- On Thu, 11/24/11, Gary LaPook <email@example.com> wrote: