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    Re: "Vernier acuity" of horizon IC tests
    From: Greg Rudzinski
    Date: 2009 Jul 8, 10:05 -0700

    I find that my Pentax binoculars and camera lenses show superior
    images when compared to any of my sextant scopes. Sextant scopes may
    be compromised(intentionally?) in the areas of chromatic and spherical
    aberration. If so then I would hope for good reason and not to just
    save a nickel per unit on construction.
    On Jul 7, 12:57�am, "George Huxtable"  wrote:
    > Bill Morris reports an nice series of tests of index-error variation when
    > viewing a distant land-horizon..
    > To summarise
    > naked-eye set 1: �mean error = 1.467; � SD = 0.458
    > X4 Gal. � � � � � � � mean error = 0.743; � SD = 0.187
    > X6 Kep. � � � � � � mean error = 0.593, � SD = 0.129
    > naked-eye set 2: �mean error = 1.30; � �SD = 0.415
    > The surprise, to me, is not in the difference in the scatters, but in the
    > difference between the mean values of zero-error.
    > Those statistics strongly suggest (though are not yet conclusive) that
    > there's a real difference between the index zeros, depending on the
    > telescope that's in use. If that's really the case, can anyone suggest a
    > possible physical cause? It eludes me.
    > contact George Huxtable, at �geo...@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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