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    Mirror Artificial Horizon -- Revisited Once Again
    From: Bruce J. Pennino
    Date: 2012 Sep 20, 18:32 -0700

    Hello All:

    After reading most of the very helpful postings, particularly those last November,I've decided to try to make a large AH because I really don't want to use a commercial small one. I'm hoping to use it on stars.

    My first effort was "quick and dirty": I used some small planed boards to make a small raft. The raft was symmetrical and I located the center of gravity CG (probably not to the precision required), and placed a low cost 6 inch diameter mirror on the CG.The mirror was in a frame that could not be removed. The results of my sun sights on a windy day were extremely poor. But the raft and mirror simulated a rocking boat and made it possible to do sights. My first question, can a first surface mirror on a reasonable size raft in a baking dish work?

    I have access to a machine shop, steel plate, aluminum etc. My next option is a 3/8" steel plate bigger by 3 inches all around a front surface mirror. I'll use 3, 3/8" leveling screws. I've found at a local mirror shop where 10"x16"x1/8" front surface mirror can be purchased for $25. Seems reasonable to me. I can also buy 6"x8"x1/4" front surface mirror at sciplus.com for $27. Recommendations?

    I could not find the recommended place to buy spirit level vials. There are many sources. Suggestions for source?

    I would use 2 vials. One on the vertical centerline and one on a left-to-right centerline. OK? I understand for reasonable accuracy of a sight (a few minutes) I need a vial with 0.75mm/m (2.4 minute of arc) precision (or accuracy or both). Do I need 0.5 mm/m (1.8 minute of arc? For overall ease, should the spirit vials be at least 4-6 inches in size?

    Thanks for the help.

    Bruce
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