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Re: Why are NA sight reduction tables not popular?
From: Gary LaPook
Date: 2012 Apr 9, 01:41 0700
From: Gary LaPook
Date: 2012 Apr 9, 01:41 0700
Interesting point you bring up about using the pole as the AP. Interestingly, the law of cosine formula does produce the correct Hc but that is trivial since we all know that Hc = Dec at the pole. In the law of cosines computation the first term becomes simply sin Dec and the second term drops out because cos 90 = 0 leaving the formula as: sin Hc = sin Dec Hc = Dec All the azimuth formulas blow up because the only azimuth available at the north pole is south. Both the N.A. and the common formula fail because LHA is undefined since there is no longitude at the pole. The Power squadron formula fails because the dreaded "divide by zero" error. None of this is a surprise because we all know that you don't use azimuth for plotting an LOP when using the pole as the AP, you use GHA as the proxy for azimuth. So the computation for celestial using the pole as the AP reduces to: Hc = Dec A= GHA gl  On Mon, 4/9/12, Geoffrey Kolbe <geoffreykolbe@compuserve.com> wrote:
