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    Latitude by Lunar Distance
    From: Wolfgang K�berer
    Date: 2006 Nov 10, 01:31 -0800

    Dear all,
    
    while looking for more information on George's problem of when the drum
    sextant was introduced, I stumbled over an article outlining the
    procedure that Frank invented. It is:
    
    J�ger, M.
    Eine astronomische Ortsbestimmung ohne Kimm oder Libelle durch
    Ermittlung der H�henparallaxe des Mondes.
    in: Annalen der Hydrographie und Maritimen Meteorologie, Jg. 40 (1912),
    541 - 544.
    
    So the idea is not exactly original or new (94 years) and has been
    published in a peer-reviewed journal before, I am sorry to say.
    
    Regards,
    
    Wolfgang
    
    Alexandre E Eremenko schrieb:
    
    > This method is essentially based on the Moon parallax.
    > (Imagine that the Earth is very small. Then the
    > method will not work: all lunar distances are
    > the same, independently of your place on a small Earth).
    >
    > To estimate the accuracy, notice that the ratio
    > of the distance to the Moon to the Earth radius is
    > 60 (very roughly). So the loss of precision due to the
    > method is by the factor of 60 under the most
    > favorable conditions.
    > These most favorable conditions are:
    > a) The Moon is near zenith, and
    > b) The two directions Moon-star are perpendicular.
    >
    > So under these conditions, the method is less accurate
    > than the usual Lunar distances by a factor of 2.
    > If the Moon's altitude is 30,
    > multiply by enother factor of 2.
    >
    > Now it is hard for me to believe that one can
    > measure distances with 0.1 or even 0.2 accuracy
    > permanently and reliably:-)
    > Some results posted by Frank seem to show that he can,
    > but it is still unclear whether he posts his best
    > results of average results:-)
    >
    > I still have no definite opinion on this matter,
    > but my analysis of observations of Cook's expedition
    > seems to indicate much lower accuracy than 0.2'
    > And this was done from the ground,
    > by professional astronomers, possibly with the best
    > sextants ever made (?)
    >
    > The Lunar method was advertized as having approx 1/4 of
    > a degree accuracy. This I believe.
    > Then the lunar-with-chronometer-but-no-horizon
    > method has probably 1/2 degree accuracy or so.
    > 
    > Alex.
    
    
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