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    Re: Using a mirror fo an artificial horizon
    From: Bruce J. Pennino
    Date: 2014 Dec 30, 12:47 -0500
    Ordinary mirror glass is fine. I’ve never bothered to use the first surface glass I purchased years ago. I’m probably in the minority, but I use a cheap Empire torpedo level...$13 or 14 USD. Accuracy, if you use proper procedure,  can be as good as plus or minus 2 NM, but 3 – 4 or so is common with a hurried setup.


    From: David Pike
    Sent: Tuesday, December 30, 2014 11:06 AM
    Subject: [NavList] Using a mirror fo an artificial horizon

    Another fail I’m afraid.  Everything was perfect apart from one thing.  The surface of the oil, which was as high as I dare pour it, was too far below the edge of the tray for today’s low sun to be seen over the edge of the tray.  I also got a wet bottom sitting on the snow.  I’m thinking of getting a decent plate glass mirror from a charity shop and attaching it to a board with three screw levellers like the ones on an astro compass to make a device similar to that which appears to be being used by Amundsen’s colleagues close to the South Pole in the classic photo.  http://www.photolib.noaa.gov/bigs/libr0352.jpg  Has anyone experience with this type of artificial horizon.  Will I get problems with multiple reflections from the front and rear of the ¼ inch thick mirror glass?  Will cheapo Amazon spirit levels, suitably mounted, be sufficient for levelling?  Wikipedia seems to have some advice on levelling accuracy under ‘Spirit Levels’.  Dave

    I'd like to answer this, but I got a clear sky, I got the sun, I got no wind, I got a bowl of water, I got a tray of oil, I got a sextant, and it's 11.43. What am I wasting time on here for? Dave


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