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    Re: Perpendicularity check
    From: George Huxtable
    Date: 2004 Sep 24, 00:00 +0100

    Alex Eremenko wrote:
    >I am using the "Complete on board Celestial Navigator" which lists
    >the Sun position with only 1' precision. I hope that more precise
    >Almanach data will permit me to explore the ultimate sextant
    and Frank Reed commented-
    >By the way, I think the "Complete On-board Celestial Navigator" is very
    >clever, and its accuracy is sufficient for the realities of standard late 20th
    >century position line navigation.
    Users of Bennett's "The Complete On-Board Celestial Navigator" need to be
    aware that under certain circumstances, for bodies which are roughly East
    or West of the observer, the Azimuth table can give results that are very
    significantly in error, with errors many times greater than the "one or two
    degrees" quoted by the author; a defect that he has acknowledged.
    There has been much previous discussion on this matter on the Nav-L list,
    some of it highly acrimonious, which I don't intend to stir up again. But
    newer joiners to our list may be unaware of certain criticisms of Bennett's
    tables, which in other respects may indeed be admirable.
    However, I refer those interested to postings in Nav-L archives around 3
    March 2003 and subsequently, under threadnames such as "The Complete
    On-Board Celestial Navigator Second Edition", and perhaps also in early
    September 2003, under "Principles and being practical".
    And I recommend that navigators use some other method than Bennett's
    Azimuth Tables (for example his Weir diagram) for azimuths that are within
    15 or 20 degrees of due East or West.
    contact George Huxtable by email at george---.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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