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    Plot of my lunar errors
    From: Peter Monta
    Date: 2013 Jul 31, 06:50 -0700

    Attached is a plot of the errors in my lunar observations over the
    past couple of weeks.  They were reduced with Frank Reed's online web
    calculator.  The sextant is an Astra IIIB with 6x30 prismatic scope.
    The individual sessions are outlined in beige.  The first session is
    pretty much a disaster due to two things:  the telescope was
    miscollimated by about two degrees, and even on top of that, I was not
    properly centering the object in the telescope's field of view, not
    being sufficiently aware of the criticality of doing that.  I used my
    eyeglasses for this first session---the eye relief of the scope was
    insufficient for me to see the edges of the field of view, and so I
    ended up looking through pretty much a random segment of the field of
    view.  Not good.  All subsequent sessions were without eyeglasses and
    the telescope focus adjusted accordingly; the image quality suffers a
    tiny bit because of about 1 diopter of astigmatism, but overall it's a
    After the second session, I felt I had this thing nailed, but alas, it
    was not to be.  I think there are still some residual collimation
    problems (I wish the scope had a reticle), and perhaps some micrometer
    worm error and arc error mixed in, though that's just a guess at this
    point.  I've also plotted the errors against complete angle and
    against angle modulo 1 degree, and nothing really stands out.
    I hope this is useful as an example of what to expect on the early end
    of the learning curve.


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