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    Re: Fw: Letcher page 103
    From: George Huxtable
    Date: 2010 Feb 10, 23:51 -0000

    --- On Wed, 2/10/10, Greg Rudzinski  wrote:
    
    > From: Greg Rudzinski 
    > Subject: Letcher page 103
    > To: hannoix@sbcglobal.net
    > Date: Wednesday, February 10, 2010, 10:56 AM
    > Hanno,
    >
    > Thanks for the forwarded web book by Letcher. Page 103 has
    > a most clever way to check a chronometer at sea. When doing
    > the Dreisonstok method I only solve for Hc then use a
    > standard 10" K&E slide rule to solve for azimuth using
    > the formula cos dec x sin meridian angle / cos Hc.
    
    ===============
    
    However, that procedure is VERY vulnerable to an error in assumed dip;
    particularly so, because of the use of opposite azimuths. Each arc-minute of
    dip error results in an error of about 4 minutes of time.
    
    George.
    
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
    
    
    

       
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