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    Re: camera sextant?
    From: George Huxtable
    Date: 2010 Jul 6, 21:54 +0100

    Greg wrote, about the errors involved in his calibration measurements-
    "The 2700 pixel point could be an outlier. I'll give it a look."
    Sorry; my mistake there. The point I was suspicious of, as being somewhat
    out of line, was the one at 2300 pixels span, not at 2700, as I wrote in
    "The graphed data for both lenses is only good to plus or minus 0.8' moa
    because of pixel measurement, refraction, dip, horizon quality, and time
    uncertainties.  Going after moa tenths may not be worth the extra formula
    calculating effort."
    I wasn't suggesting that Greg should try to reduce the error in those
    numbers for moa / Px. I can see that they have been acquired with great
    care. I just wanted to see what scatter to expect, in order to put in some
    (horizontal) error-bars, on the points that were plotted for the 100mm lens
    Not all the error, estimated by Greg, will be random error, giving rise to
    scatter. But taking his figure of 0.8 arc-minutes as though it is, that
    would give rise to a horizontal error-bar extending about one square on his
    graph to either side of that point plotted at 2300. And somewhat similarly
    for all the other points. So, statistically speaking, there's no great
    justification for snaking that line-of-fit exactly through those points, as
    was shown.  And that point at 2300, the most discrepant, is only around 2
    standard deviations off the "plausible line" that I had sketched in, so it
    doesn't exactly rule it out..
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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