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    Re: Mirrored Artificial Horizon
    From: George Huxtable
    Date: 2003 Nov 2, 19:04 +0000

    Geoffrey Kolbe wrote-
    >For those following this particular thread, I will just come back and
    >defend my analysis of Kieran Kelly's problem, to which George took exception.
    >George's analysis is quite correct, as far as it goes, but I think his
    >analysis is too simplistic. He has taken a very particular scenario for the
    >topology of the mirror, (which we do not know). When he says he has chosen
    >dished or spherical shape, he has in fact analysed it as a cylindrical form.
    No, it was INTENDED to deal with the spherical case and I think it does so.
    It also covers the case of cylindrical distortion, or its component of
    curvature along the azimuth in which a sextant altitude is measured.
    >I think that if a weighted analysis was done over the possible topologies
    >of the mirror, it would turn out in the end to be quite similar to the
    >resolution analysis which I used. I think such an analysis would return a
    >quite similar result in the order of 0.1 arc-minute for the mean angular
    >deviation we should expect for a random 2cm diameter section of a mirror
    >having diameter 14cm and flat to 7 wavelengths. I may be out by a factor of
    >two or so, but I would be surprised if it was more than that.
    Geoff and I have looked at this matter from rather different viewpoints and
    have arrived at rather similar conclusions, and I am happy to shake hands
    with him about that.
    >That said, George and I both agree that Kieran should not worry about the
    >flatness of his mirror.
    We concur!
    contact George Huxtable by email at george@huxtable.u-net.com, by phone at
    01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
    Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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