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    Re: Ebay kollsman periscope sextants
    From: David Pike
    Date: 2018 Jun 7, 00:55 -0700

    the cell (see attached).  Rather than using a mirror to reflect the light up into the cell from below,  you could use a prism to bend it down to view the cell from above. Placing the lamp behind the cell would give you a dark circle against a bright background. So it could be done. throughThe A-12 had a different type of light path than the Kollsman – you don’t view the star

     Paul
    That would be an interesting experiment.  I've got an A12 in the wardrobe.  Before going any further, first step would be to place a small black circle on top of the bubble cell and see what you see through the sextant.  Then see how the Sun looks against it,  Then on a stary night try against a planet and then a star. Does the upper glass in the A12 form any part of the collimation? You can take the bulb out for the test against the Sun.  You'd need it in for the test against the stars.  DaveP

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