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    Re: Hybrid Artificial Horizon
    From: Bill B
    Date: 2008 Sep 14, 01:15 -0400

    George wrote
    > I don't think that would work. With an open bottom, all the form-stability
    > of a flat box shape would be lost. It would be a bit similar (but the other
    > way up) to the loss of stability that occurs on roll-on vessels when they
    > get water sloshing around on the wide vehicle deck.
    Speaking of sloshing water, was this device protected from the wind in some
    manner?  It is a significant problem if the water itself is not perfectly
    I had very good results with a roughly 10" x 4" plastic storage container
    (with a positive 4-latch and O-ring-seal lid) filled with 50-weight motor
    oil with black woodworker's oil-soluble dye added to the oil.  3/4 full, it
    provided a long surface good for low altitude observations.  The ink-black
    oil had no problems reflecting the navigational stars even with some light
    The drawbacks:
    Wind would effect the surface of the oil, so it needed a glass cover.
    No matter how careful I was about cleaning the rim of the vessel, oil got on
    the outer regions of the glass and cleaning it up to my standard was a pain
    in the rear.
    If I put small shims between the glass and the vessel rim to stop the oil
    transfer, wind could still cause minor ripples on the oil surface.
    Testing was necessary to be certain the faces of the glass were parallel.
    The oil was so highly reflective, it was too easy to mistake the image
    reflected from the cover-glass surface for the image reflected from the oil
    The glass surface was not necessarily parallel to the oil surface.  On the
    plus side, this could assist in distinguishing between the glass and oil
    reflected images. Not a big deal to use an inexpensive hardware-store bubble
    level to get the container and glass parallel within cel-nav tolerances.
    Upsides: It is cheap, it works well, and no problems with water vapor
    condensing on the glass during sun shots.
    Downsides: It is messy, and you don't want to spill any of the oil/dye
    mixture on your garments, shoes, floor, driveway or lawn.
    Bill B.
    Navigation List archive: www.fer3.com/arc
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