From: Ducruy Jacques
Date: 2015 Aug 4, 03:13 -0700
Thank you very much : your study is very clear.
The only difference with the Reed's table : Hall give only Log Cos, Reed's give directly log cos and log sin : so, you can calculate the azimut by sinus formula easily (but with lack of precision is Z is near to 90°).
It is also interesting to study the evolution of versine formule :
Douwes formula : Sin Alt = Sin Mredian Alt - (Cos D Cos L Vers HA)
Lynn formula (1827) : Vers DZ = Vers (L-D) + (2 cos D Cos L Sin² HA/2) ... or : 2 sin² HA/2 = Vers HA
Conclusion : the formula used by Hall is the same of the formula of Lynn !
And we can adapt this formule with haversine :
Hav DZ = Hav (L-D) + (Cos D Cos L Hav HA) => Davis formula ?