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    Re: sextant index error measurement
    From: George Huxtable
    Date: 2006 Nov 12, 13:48 -0000

    Thanks to Jim van Zandt for correcting my posting [NavList 1613],
    which was itself an attempt to correct my earlier posting [NavList
    And I agree with him, that this time it is indeed right; that the
    offset between the two viewlines from a sextant, when it's set to 0
    degrees, will be 2 d sin A, in which d is the distance between the
    parallel reflecting surfaces (allowing for the refractive index of any
    intervening glass) and A is the tilt of the horizon mirror, from being
    at right-angles to the axis of the telescope. Sorry about getting it
    wrong twice before.
    Funny, isn't it, how I had just written, in [NavList 1666]-
     "This list acts an an almost-instant peer review, for
    which I have been truly grateful when it has found flaws in my own
    arguments; a more frequent occurrence than I wish to recall."
    and then to have it exemplified so graphically! It's good to see how
    effective this list can be, at detecting rubbish.
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    To post to this group, send email to NavList@fer3.com
    To unsubscribe, send email to NavList-unsubscribe@fer3.com

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