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    Re: Lewis & Clark's artificial horizons
    From: Bruce Stark
    Date: 2014 Jan 2, 17:39 -0800

    Must be something wrong with the way I'm using the posting code Frank gave me yesterday. I've tried twice since this morning to answer Greg Lucfi's question about how Lewis and Clark got latitude with an artificial horizon in late spring and summer. I'll keep trying.

    Although they used Patterson's mirror horizons a few times to get latitude from Polaris they normally used their wooden quadrant with the noon sun, turning the quadrant around and using it's back- horizon glass when the sun was above 45°. Theoretically they could measure angles on up to 180° this way. But it must have been a tricky procedure, and it doesn't seem to have been very accurate. Maybe someone who owns a quadrant with a back-horizon can fill us in on this.
    Bruce
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