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    Re: Level vials for mirror artificial horizons
    From: Bruce J. Pennino
    Date: 2013 Mar 12, 18:25 -0400
    When I made my mirror AH last year I was all set to buy the commercial bubbles/vials.  But I discovered that Empire makes a standard compact torpedo level that is only 9 inches long.  Its stated precision is 0.0005 inch/inch or 1.7 minutes of arc.  At $15. US
    I tried it, and it works great. I made a little foam/felt bag and it goes into AH box.  I level mirror end to end, rotate level and bring the bubble 1/2 way back. Then do leveling in other direction. Recheck first direction leveled. Quick.
    I've taken sights at the same location, same day with normal horizon and AH with out any significant difference in results.  Easy. By the way, I also bought a first surface mirror and a less expensive standard  mirror . I normally select the brightest stars or moon, and the ordinary mirror is good enough. One of these days I'll use the first surface mirror on some secondary stars.  My mirror is
    about 6" x 9". If I did it over, I'd probably go 9"x9". 

    ----- Original Message -----
    Sent: Tuesday, March 12, 2013 1:54 PM
    Subject: [NavList] Level vials for mirror artificial horizons

    In previous postings I described how very sensitive spirit levels can be made by anyone. It is easier and cheaper in the long run to buy commercially made level vials. Here are two sources:
    Level Developments in UK sells 13 second vials for $50.00 each.
    L. S/ Starrett CO. in USA sells 10 second vials for about the same.
    The vials can be put into protective bases with brass 1/2 round feet than can be sanded for fine tuning. An example is attached.

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