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    Re: Principles and Being Practical
    From: Peter Fogg
    Date: 2003 Sep 6, 08:47 +1000

    ----- Original Message -----
    From: "George Huxtable"
    
    To those of us who have
    > done all that introductory stuff, years ago, some of the fine-points and
    > abstruse-topics and historical-questions are of great interest, and the
    > Nav-L list is our method of communicating with each other about it. Would
    > Peter Fogg deny us that?
    
     No. And I enjoy them myself. Don't miss the point.
    
    As for the Azimuth Tables, there are instructions in the book to be followed
    to deal with the potential problems when the bearing is close to 90 or 270
    degrees. A common sense approach, remembering that the whole idea is to
    keep things simple on-board, is to give the tables a miss and use another
    method (provided) in these rare enough cases. There is no need to make a
    mountain out of a molehill. To say they are 'VERY bad' is a gross
    exaggeration, at the VERY worse they might be only slightly naughty.
    
    When taking sights the hand bearing compass is around my neck, and the
    compass bearing of the star or planet noted with the other data (I might
    need the corrected [true] bearing or azimuth to find out which body it is,
    through the Prediction and Identification Tables). This corrected compass
    bearing is accurate enough to use for plotting a sight, being out by a
    degree or two makes little enough difference to the LOPs, and thus the fix,
    in most cases. So the Azimuth Tables or the Weir Diagrams are mainly useful
    as a checking tool.
    
    Working the other way, knowing the azimuth accurately, is useful to check
    for compass deviation, the particular effects of each individual boat that
    alter the compass reading.
    
    The advantages, in most cases, of having simple 'look up' tables immediately
    providing an azimuth accurate enough for the purpose more than outweighs
    any theoretical shortcoming they may have in some extreme example.
    
    So with a common sense and practical approach one can approach the Azimuth
    Tables with calm and confidence. Its a bit of a non-issue.
    
    
    

       
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