NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Ducruy Jacques
Date: 2013 Jun 12, 08:44 -0700
Hello Peter,
The Borda's formula was also used in England ; it is used for calculate the hour angle (HA) (and for the sun : hour angle = apparent time (or "true time" in France).
Borda's Formula
sin² HA/2 = (Sin (S-A) Cos S) / (Cos L Sin DP)
with :
A = true altitude
L = DR latitude
DP = polar distance (or 90° -/+ Dec)
S = (A + L + DP)/2
I add that the "Pagel coefficient" (Pagel was a french navy officer) give the error of HA produce by one minute of error on latitude :
Pagel coefficient = Cotg azimut / Cos latitude
Jacques
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