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## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Office Hours Ageton Classic
From: Huub Robroek
Date: 2021 Feb 11, 09:59 -0800

Hi Greg

I have been doing some old exercises with "traditional" sight reduction to compare them with Ageton Classic. I encountered a problem in an exercise with LHA = 303 deg.

In trying to use a value for t from LHA I thought that t = LHA-180 = 123 deg might work. If I continue with this value of t I then apply the rule for t>90 deg for the value of B-1 cos. This does not result in the correct value for Hc (as I somehow expected). See attached my calculation. I only find the correct result when I apply the rule t<= 90 deg. Am I missing something? Somewhere there must be a separate rule for LHA > 180 deg....(?):

I have been running around in circles, looking at sin and cos values, and formulae, and went through various Ageton posts, but did not see any reference to a situation like this. I assume the solution is simple. A hint in the right direction is much appreciated.

Huub

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