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    A-12 & Kollsman test results
    From: Paul Hirose
    Date: 2003 Jan 21, 13:07 -0800

    Results from taking 25 sun shots each with bubble sextants on my
    porch. Did not use either instrument's averager. The sextants were
    completely hand-held. The "correct" altitudes were obtained from the
    USNO online celestial nav calculator. Index corrections for each
    sextant were based on bias noted in previous sets of sights. For
    timing I just glanced at my wristwatch when the sight picture looked
    right. After recording all sights I corrected for watch error.
    Link A-12: bias 0.0', standard deviation 1.8'
    Kollsman periscopic: bias +1.5', std dev 1.4'
    I used a +1.4' IC for the Kollsman; looks like I should have used
    zero! Will continue to use the same IC and see if those results
    The Link's results had no significant bias; apparently the +11.6' IC
    I'm using is just right. I have no idea why the IC is so large. The
    instrument looks near mint and the altitude mechanism feels fine.
    I find the Kollsman more fun to use because it's the more
    technologically complex instrument. Plus I can adjust the bubble size.
    (The A-12's is bigger than I like.) However, its non-averaged results
    aren't much better. But reading the altitude is a lot easier since the
    minute graduations are about the same size as degrees on the A-12. I
    use a magnifying glass to read that one.
    Physically the A-12 is easier to manage due to its light weight and
    the viewing position. You hold it in front of your chest and look down
    into it. The Kollsman weighs 7.4 lb and must be held at eye level.
    It's not bad, though, even on a 2-minute averaging run. The mental
    effort maintaining coincidence for that long is about as tiring as the

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