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    Re: Happy Equinox Day
    From: Peter Fogg
    Date: 2007 Mar 22, 16:33 +1100

    > > and then compare this pattern with the (in this case)
    > > horizontal slope?
    >
    > Eh? Wouldn't a graph of the sights still follow the familiar parabolic curve
    > leading up to and then following local noon? I wasn't aware that the
    > declination being almost zero would have any affect on that (of course, the
    > slope of the LOP *is* horizontal at meridian passage, but that's the case
    > any time of the year as far as I know...).
    
    Over a few minutes spanning LAN there is very little change in the
    body's altitude - they used to say the sun tends to "hang in the sky"
    at this time.
    
    So differences in recorded altitude over those few minutes are mostly
    caused by random errors in observation. By comparing a graph of them
    with your horizontal line it may be possible to derive a better
    altitude to adopt for calculation of your latitude than any of the
    recorded sights (see: "An example of a slope", 10 March 07) .
    
    You could also (if you had a reason to) calculate the standard
    deviation of those sights, which could be useful in terms of analysis
    of the resulting position line (see recent thread on "Cocked Hats").
    
    Since you have the sights recorded it might be informative to go back
    to them and try it out. This particular case lends itself easily to
    the technique, since you don't even need to calculate a slope - it is
    effectively a horizontal line over five minutes of time spanning LAN.
    
    Let us know the results ...
    
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