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    Re: Old style lunar
    From: Alexandre Eremenko
    Date: 2004 Dec 15, 16:28 -0500

    Ken,
    Thanks for your explanation.
    I will think about these numbers,
    but I have to leave now for 3 weeks,
    and don't know whether I will have access
    to e-mail and web till Jan 8.
    
    On Wed, 15 Dec 2004, Ken Muldrew wrote:
    
    > On 15 Dec 2004 at 12:39, Alexandre Eremenko wrote:
    >
    > > Why did not he measure altitudes?
    >
    > With a sextant and an artificial horizon one can
    > only measure altitudes up
    > to 60?. That is enough for this series,
    > and probably many more, but
    > Thompson (and his contemporaries) never measured altitudes.
    > It just wasn't
    > part of their procedure.
    
    I afraid do not understand this "procedure".
    He took a time sight anyway.
    Why did the procedure include a separate time sight
    instead of just measuring the altitude of the star
    involved in the lunar?
    This is equivalent to a "time sight", is not it?
    
    My second question is what exactly the procedure was
    for computing the alitudes?
    
    To compute an altitude you have to know
    the declination and right ascention of the body
    (from the almanac) and LOCAL time at the place
    of observation.
    If you know local time, no DR longitude is involved.
    (I assume that he knew his latitude with sufficient precision).
    I also assume that the local time was known from the time sight.
    
    If THIS was the "procedure" for the computed altitudes,
    then I don't see how DR made influence on his computation.
    
    Or the procedure was different?
    
    
    Alex.
    
    
    

       
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