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    Re: Moonrise video
    From: Brad Morris
    Date: 2013 Apr 30, 11:54 -0400

    van Asten

    you wrote
    "Any ex-marine air navigator of the era certainly knew about the for the sun zero altitude refraction , then figured 37 arcminutes . Be it not from H.O.208 or other tables , every textbook and the nautical almanacs contained chapters on the subject"

    Assuming a nominal value for refraction of a body on the horizon is a far different matter than using that to produce a line of position.

    I challenge you to produce a single authoritative reference (like HO208) which illustrates your technique of a line of position from a zero altitude celestial body.  Just one.

    You wrote
    "mr.Noonan´s supposed ability to derive a more or less accurate geographical position from observing sunset and sunrise "

    One does not get a geographical position from an observation of a celestial body, one gets a Line of Position.  The uncertainty due to refraction, will yield great variability in that LOP, making it useless.  Hence the reason that the navigator is cautioned not to use altitudes below 5 degrees

    I challenge you to produce a single example of the derivation of a Line of Position from a zero altitude celestial body from Noonan's existing log books.  Just one.

    +++

    Mr. van Asten:  You cannot make assertions without providing reference, otherwise we may think less highly of your assertion.  You get to prove it, and if you cannot, then you get to retract your assertion.  Its a form of learning.  We admit when we blunder and in doing so, learn from our mistakes.

    If you wish to pursue this technique as a new and novel method, then it must with stand mathematical scrutiny.  Refraction at the horizon causes this technique to be highly questionable.  If you think otherwise, then you are challenged to show, by equation, the method and expected accuracy. 

    If you wish to pursue this technique as contained within historical context, then reference to it must be contained in the historical record.  You have been respectfully challenged to to so.

    Brad

    On Apr 30, 2013 9:02 AM, "h.a.c. van Asten" <hac.vanasten---.com> wrote:

    Any ex-marine air navigator of the era certainly knew about the for the sun zero altitude refraction , then figured 37 arcminutes . Be it not from H.O.208 or other tables , every textbook and the nautical almanacs contained chapters on the subject . Conyers Nesbit , professional navigator , in articles (*) and a book refers to mr.Noonan´s supposed ability to derive a more or less accurate geographical position from observing sunset and sunrise . It is not even necessary to observe for the instant : if the time-position group is precomputed and sunset-sunrise superficially observed from an aircraft , one acquires an indication for being with acceptable uncertainty in the vicinity of the precomputed coordinates pair . Mr.Noonan may have used this fashion when near Nukumanu Island he announced his position at 0718 GMT (mr.Chater´s watch time) , whereas actual sunset was at 0719:30 GMT , as mentioned in the addenda on EJN articles of July 2008 and April 2011 . We do not know it by certainty , but he may have also used it for sunrise in the roads of Howland .

    (*) Aeroplane Monthly , Jan and Feb , 1989 .
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