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    Re: Artificial horizon question
    From: Peter Hakel
    Date: 2009 Apr 20, 17:11 -0700
    I strongly suspect that John and I have the exact same artificial horizon and sextant.  Did the sextant come with David Owen Bell's booklet and William F. Buckley DVD?    Just curious...  :-)

    I don't seem to have a problem bringing and keeping the two disks together.  For the reflecting liquid I used water which is not bad.  I had better results with dishwashing liquid.  Liquid soap is even thicker but a bit too much for me; bubbles tend to get easily trapped on the surface and it's a mess to clean up.


    From: "JKP@obec.com" <JKP@obec.com>
    To: NavList@fer3.com
    Sent: Monday, April 20, 2009 4:45:23 PM
    Subject: [NavList 8006] Re: Artificial horizon question

    George, GL and Peter,
    Thank you all for continuing to offer helpful advice.  To answer some of George's questions about the horizon I am using, it is the inexpensivce Davis model, and has a sloped-roof type of cover, with solid plastic sides ("gables" if you will) and clear or colored plastic panes.  The panes appear to be quite flat as far as one can tell by looking.  No doubt they are cut from large sheets after emerging from a pair of rollers set to a precise tolerance.  Perhaps in cooling or handling they acquire some irregularity.  Moreover, the image is passing through the panes more or less normal to the surface.  It may be refracted a bit going through, but I don't think I'm seeing and extra reflection, as I might if I were reflecting the sun off a stack of horizontal plates.  Again, it may be reflecting from the top and bottom of the pan, so I will try some light-deadening measure on the bottom.

    When I see the reflected sun in the pan of mineral oil, it is very distinct and solid, and depending on the cover I have over it, may be bright yellow.  As I bring the sun down from the sky, again viewing through various filters, it will appear to the right of the yellow reflected image and will be, perhaps bright green or blue (depends on the filter).  There is no mistaking which is which, and no particular impression that either image is double.  They will be separated horizontally anywhere from two to four or five diameters apart, but as I squirm and squint, fiddle with the telescope focus and the micrometer, and try to hold my toes just the right way, they drift slowly together, then apart again. It's much like watching the little floating debris on the surface of your eye; you can sort of chase it in one direction by eye-rolling or will power, but it always wants to slide back.  But I digress.

    I'll give your suggestions a try next time I'm out.  I'm especially grateful that some of you pointed out the advantage of getting the images edge-to-edge rather than totally coincident.  Let's see if this improves my results!


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