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    Re: A-12 Bubble Sextant (Octant)
    From: Jean-Philippe Planas
    Date: 2014 Feb 11, 23:01 -0800

    I am afraid the easiest way to proceed would be to buy a new bubble illumination assembly including the rheostat. The best way would be to purchase a wrecked A12 on Ebay making sure the bubble illumination assembly is present and to canibalize it.I own several A12s presently but don't consider parting with them at the very moment.
    Good luck

    On Monday, February 10, 2014 8:27 PM, J.M. Kalouguine <kaloujm@free.fr> wrote:

    Thank you for the tip, but unfortunately in spite of all of your advise I've tear down the zinc tube to peace... Certainly to brutal! I collect the complete rheostat . Do you know if it is possible to by an other one or rebuild the body and re using the original rheostat?
    This message was posted in reply to:
    From: Jean-Philippe Planas
    Date: 2010 Sep 22, 22:57 -0700

    To make it short.

    If the bubble illumination assembly is not inserted in the sextant you can remove the bubble assembly by just twisting it a degree or two and pulling on it.
    If the bubble illumination assembly is present, remove it first as the bulb interferes with bubble assembly when you pull it out.
    If the bubble illumination assembly is stuck, then proceed as descried here;

    To adjust the sextant, just back off the screw (with an Allen or similar wrench) that links the index mirror on this axis to free the mirror and reposition it to a correct postion for instance using polaris or during LAN. When the bubble is centered and the vernier indicate the precomputed reading, tighten the screw back.

    You may then fine tune the index error by adjusting the vernier which is position with two screws at boths ends.

    Good luck and please keep us posted on your progress.

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