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    Re: Latitude and Longitude by "Noon Sun"
    From: Frank Reed CT
    Date: 2005 Jun 14, 21:16 EDT
    George H you wrote:
    "There's another phenomenon that a navigator might not expect when sailing
    in gusty/squally conditions in a North or South direction near noon. If his
    vessel is speeding up in the puffs, then slowing in the lulls, then so will
    his rate of change of Sun altitude due to those changes in speed. That
    changing slope has to be added to the expected parabolic change in Sun
    altitude caused by the Sun's transit through the meridian. And the end
    result is a wavering of the curve of altitude with time, about its peak. In
    an extreme case, the Sun could show more than one maximum altitude.

    I don't suggest that that's going to be a cause of serious error. The
    effects on the resultant wavering parabola can be averaged out, rather
    well, by the proposed folding of the graph, particularly if the series of
    measurements extends well away from noon"
     
    As long as you're considering more intricate scenarios like this one, it's a good chance to point out the advantage of the simple altitude adjustment technique that I've already outlined. Imagine a scenario where you're sailing along with a nice breeze making 7 knots from the beginning of your sight series twenty minutes before noon until right around noon when, suddenly, the wind dies. Though you might need to think through a few little details, by adjusting each sight individually, this case can be handled easily.
     
    You asked:
    "I haven't seen any response from Frank to this suggestion, and wonder if he
    thinks that it is perhaps wrong, or negligible."
     
    At this point, I think it's a minor detail, but I haven't devoted much time to it (so maybe I'll change my mind later!). What little time I have spent on this 'lat/lon at noon' business has been focused on refining the small stuff and trying to reach a happy balance between economy of paperwork and economy of paper (that is, I don't think there's advantage to this method if it requires lots of tricky calculations, and at the same time, there's not much advantage if it requires purchasing and carrying a volume of tables).
     
    -FER
    42.0N 87.7W, or 41.4N 72.1W.
    www.HistoricalAtlas.com/lunars
       
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