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    Re: Bligh's noon by chronometer
    From: Jeremy C
    Date: 2010 Jun 3, 07:46 EDT
     
    George wrote:
     
      It could be taken up to an hour or more either side of noon, whenever a glimpse of the Sun appeared
    through the clouds.  And then, the latitude could be readily calculated
    from the altitude at that moment, knowing the time difference from noon,
    using the Ex-meridian Tables. That was primarily what those tables were
    for.

    ======================
     
    Were the tables altogether different than modern tables?  The current Bowditch tables don't calculate beyond a meridian angle of 7 degrees, or around 29 minutes of time.
     
    The formula also falls apart close to noon near the equator so much so that they are not even presented.  I have run into that problem several times when trying to shoot ex-meridians when Hs is above 80 degrees.
     
    More to the point, I am starting to shoot sun at meridian transit not based on highest altitude but rather by calculated time to avoid the errors due to ship's motion.  I am getting much more accurate results in Latitude with this method.  I have always used this method when shooting the moon, planets or stars at transit.
     
    Jeremy

       
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