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    Re: Longitude by Sunset
    From: Alexandre Eremenko
    Date: 2012 May 6, 20:29 -0400

    Greg,
    
    > Would it be possible to compare an observation of the
    > Moon at 2 * then follow with an observation of the Sun at 2* from the
    > same location and height of eye to perform the time lunar you are
    > suggesting ?
    
    I suppose so. But then the exercise almost looses its purpose.
    If you have an accurate sextant, you can shoot a Lunar distance,
    and there is no point of timing the difference between Sunset and Moonset.
    
    The idea was that you only have a backstaff (wooden quadrant, plastic
    sextant, pocket sextant, bubble octant etc.), a devise with which you
    can shoot Sun or Polaris and obtain latitude to 1'-2'.
    This instrument will give you 30' to 60' accuracy in longitude
    if you use it for Lunar distance.
    
    My hope was that by timing the difference between Sun and Moon set,
    you can do better than that with longitude.
    
    The question how accurately you can time a sunset/moonset, is interesting
    eve besides this application.
    The main point of the paper I was referring to was to refute the claims
    of some historians/archeologists which like to say that various ancient
    structures (Stonehendge, Egyptiam pyramids etc.) are oriented
    very precisely to catch a ray of setting Sun on some date.
    The authors are trying to prove that it is impossible to achieve
    very exact orientation just by observing the Sunsets.
    
    So the question is interesting in itself.
    Especially intriguing is a recent statement on the list
    that "one cannot see a moonrise/set at all"!
    
    I really don't remember seeing one, but do not understand why this is
    impossible.
    
    > Unfortunately
    > I can't perform this experiment for a true
    > sunset/moonset from my location because there are islands in the way :(
    
    I am in much worth position: all I see is the trees:-(
    And need a whole day roundtrip to see even a lake horizon:-(
    
    Alex.
    
    
    
    
    

       
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