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    Re: Averaging
    From: Jim Thompson
    Date: 2004 Oct 20, 16:52 -0300

    Fred's observer sextant altitude curves look a heck of a lot prettier what I
    get from the deck of our boat at anchor on a lunch hook.  My R-values
    certainly are not 0.9999 for a straight line fit!  Obviously I need more
    I think I agree with Bill -- in real life on a small boat I would be happy
    with averaging 4-5 sights over 5 minutes.  My random observational errors
    are more likely to be much higher than any systematic error owing to
    nonlinearity in a body's motion, with the exceptions he noted.
    Jim Thompson
    Outgoing mail scanned by Norton Antivirus
    > -----Original Message-----
    > From: Bill
    > What did this beginner learn from the exercise?
    > * Alex and Herbert are correct,the error is more pronounced for high
    > altitude bodies, and they are unacceptable targets for averaging
    > except for
    > all but last-ditch efforts, especially at meridian passage; even if
    > double-second-differences and problems with the operator holding
    > the sextant
    > vertical are discounted.
    > * Shy away from averaging a body with a declination within 10d-20d of the
    > observer's latitude.  (If it would have trouble casting a
    > significant shadow
    > of the mast on the deck, leave it alone. This is cel nav SOP.

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