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    Re: Standard Deviation Question
    From: Bill B
    Date: 2013 Jan 05, 18:11 -0500

    On 1/5/2013 12:00 AM, Greg Rudzinski wrote:
    > Here are 20 index error observations of Procyon using a Tamaya Jupiter
    > with 7 x 35mm scope.
    > x = 0.575'
    > Sx = 0.1585'
    > All observations are off the arc.
    Out of context I am not sure what the above indicates statistically,
    other than you are far better at determining index error from a star,
    especially a bright star, than I am :-(
    Alex suggested I use the dimmest star I could see.  Frank posted an
    article that taught me what some submariners and others believed--pop
    out, take your shots and be done with it. (As your eye becomes dark
    adapted a point source becomes a scatter of point's or star bursts.) I
    gave up star IE checks except as a court of last resort. If I can come
    within 1' of the values I obtain with a natural horizon or sun IE check
    I'm lucky.
    I thought the excellent Celestaire 7X scope would improve my results.
    Nope. The Astra has performed almost flawlessly in other observations.
    Seems to prove the old adage, "Don't blame poor craftsmanship on poor
    tools. If you doubt it, put excellent tools in the hands of a poor
    What is of interest to me is using the figures in your 2 January post as
    an IE check vs your star IE check. Half of the difference between your
    32!64 off the arc and 32!56 on the arc is a highly respectable IE of
    0!04 or 2.4" off the arc vs 0.574' off the arc for Procyon.
    I'm very accurate and precise with star-to-star measurements as I can
    swing one through the other, but one-star IE checks are not for my old
    eyes--with or without eyeglasses.
    Bill B

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