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    Re: Z tangent formula
    From: George Huxtable
    Date: 2005 Jul 10, 22:14 +0100

    At 08:42 07/07/2005, Peter Fogg wrote:
    
    >I've taken 3 sights at random to contrast a few different (?) methods of
    >azimuth determination. The first comes from the problem Mike Burkes posed,
    >that I worked out and posted here on the 2 July.
    >
    >Sun UL Azimuth - in decimal form, and to 3 decimal places if available
    >101             'Bennett book' azimuth tables
    >100.9           Sharp nav. calculator
    >100.982 NavPac
    >100.985         Z tan formula
    >
    >The other two come from the first other worked sights to hand. Details
    >available if anyone's interested.
    >
    >Miaplacidus Azimuth
    >183             'Bennett book' azimuth tables
    >182.6           Sharp nav. calculator
    >182.637 NavPac
    >182.665 Z tan formula
    >
    >Dubhe Azimuth
    >010             'Bennett book' azimuth tables
    >010.2           Sharp nav. calculator
    >010.238 NavPac
    >010.214 Z tan formula
    >
    >So I'm convinced, pending further tests, that the Z tan formula is a valid
    >and accurate method for determination of azimuth. The small differences seem
    >insignificant. It is not significantly more tedious or time consuming to
    >calculate, given a good scientific calculator, than the other methods. This
    >is because the calculator and NavPac require quite a lot of data to be
    >entered to give a result.
    >
    >However, I do wonder whether one method or another does give a more
    >precisely accurate result, although the answer is probably irrelevant for
    >most practical purposes. Am hampered, admittedly, by not knowing what
    >methods my calculator or NavPac use. Anyone have other formulas for
    >comparison purposes? Or ideas on this?
    
    But Peter makes it difficult (indeed impossible) for anyone else to
    reproduce his calculation, by omitting mention of the values of hour-angle,
    lat, and dec that he has used. If Peter will provide that missing-link, he
    might get some more informed responses.
    
    George.
    
    
    
    ===============================================================
    Contact George at george@huxtable.u-net.com ,or by phone +44 1865 820222,
    or from within UK 01865 820222.
    Or by post- George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13
    5HX, UK.
    
    
    

       
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