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    Re: Bubble Sextants and book "Back Bearings"
    From: David Pike
    Date: 2022 Aug 5, 10:46 -0700

    Howard G you wrote:  And I suppose why my A-12 bubble will be used standing up in a field walking around to simulate “a bit” of the old days.

    Howard

    I don’t think you’ll get much satisfaction walking with an A12 or a MkIXBM.  I tried both this morning.  To be frank, at 78, it’s difficult enough getting the bubble in the middle even when I’m steadily seated let alone walking.  The MkIXBM balances well when hung up but is nose heavy in the hand only.  The Mk12 was never meant to be hung, so those WW2 USAAC Navs must have been really ‘beefy’.  If I’m struggling, I find a good place to start centring the bubble in the A12 is to look away and move it until the ridge along the top of the handle is horizontal.  That appears to coincide with bubble central.  Attempting to walk looking through either sextant has the bubble rattling around all over the place, worse than you’ve ever seen during CAT.  Also, with the MkIXBM, one or two minutes is a long time to walk without bumping into something.  As a veterinarian, you though have an advantage.  You could always remove the existing fluid from your A12 bubble chamber and inject horse tranquiliser.  DaveP

       
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