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    Re: Artificial Horizon Levels
    From: Robert Eno
    Date: 2004 Mar 28, 22:48 -0500

    Thanks Trevor,
    That makes sense.
    ----- Original Message -----
    From: "Trevor J. Kenchington" 
    Sent: Sunday, March 28, 2004 3:59 PM
    Subject: Re: Artificial Horizon Levels
    > Robert, Fred:
    > It hardly needs tables, nor even much geometry.
    > With a truly level artificial horizon, the sextant angle (after
    > correction for index error) will of course be twice the observed
    > altitude of whatever body you are looking at. With a tilted horizon, it
    > will be twice the altitude plus twice the angle of tilt (where tilt
    > towards the body observed is treated as positive, tilt in the opposite
    > direction as negative).
    > Hence, an unrecognized 30-second tilt would introduce a 1-minute error
    > into the sextant angle but that would lead to a 30-second error in the
    > estimate of altitude. The final calculation of Ho might have a very
    > slightly larger or smaller error, depending on misreading of tables of
    > refraction and so forth.
    > Trevor Kenchington

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