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    Re: Sextant mirrors
    From: George Huxtable
    Date: 2007 Oct 9, 19:58 +0100

    On the subject of whether muliple reflections within a back-silvered glass
    mirror give rise to multiple images, Fred Hebard wrote-
    | Hmm, I wonder if this shows up in artificial horizons, which is where
    | I recall (vaguely) having seen it?  No time to check now, but I'll see.
    Well, it shouldn't, if they are made of decent glass, with the two surfaces
    really parallel. However, larger pieces of glass are usually used for the
    roof of an artificial horizon, and so there might be a temptation to use
    poorer quality than for a sextant mirror. Even so, I would be surprised if
    the glass was bad enough to have enough "wedge" shape in it to produce the
    multiple images that Fred mentions. As he says, we'll see, when he reports
    back on his reflected sky images.
    On the other hand, if he uses a transparent liquid, such as plain water, and
    the bottom of the tray it's in is shiny, and not quite horizontal, then he
    will see multiple images from those different paths.
    contact George Huxtable at george---.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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