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    Problems with a mirror ah compared to a Davis Artificial Horizon
    From: Alan S
    Date: 2012 Sep 14, 14:44 -0700

    I have come to the realization that most, possibly all of the difficulties I've had trying to use a Mirror Artificial Horizon revolve around inaccuracies in leveling the assembly. The bubble level I have used is simply not sufficiently accurate for this class of leveling (10-20 seconds of arc). Using a Davis AH, I seldom have any problem with AM and PM sun shots, usually deriving a calculated fix that is well inside 5 nm of a known position (GPS coordinates).

    Given that water seeks it's own level, it is "self leveling", even here in western PA I believe, I tried floating the mirror, figuring that this would do away with the problems of mechanical leveling. Didn't work, though I got a painfully brilliant "mirror sun", I could not find the "sextant sun".

    As a check, this afternoon at about 1620, I set the two ah's up immediately adjacent to each other. With the Davis ah, I readily got a "lower limb" sun shot, sextant sun above reflected sun, Hs reading 65 degrees 20 minutes.

    I then, without changing anything on the sextant, looked at the mirror sun. I could not find the sextant sun in the floating mirror ah. Both ah's were properly oriented, which leaves me curious as to what the problem might be, the possibility of operator error is always there.

    I would like to try ah shots of the moon and perhaps stars too, which I do not be believe can be done with the Davis ah, ergo my messing about with a mirror unit, about which there have been a number of posts.

    Does anything come to the mind of readers? If so, any assistance would be much appreciated.

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