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    Re: Bubble sextant at sea
    From: David Pike
    Date: 2025 Jan 26, 11:59 -0800

    I think they must have brought the gyro version in when the U-Boats no longer dare surface in daylight or even twilight.  The gyro version must have been a struggle to work with, because it had to be run up inside the hull and then carefully handed up the ladder to the conning tower before it ran down too much. It took me a while to work out how you could see through it if the gyro was whizzing round.  Then I realised it was like a movie projector.  As long as you got a glimpse through the telescope more than 32 times a second, you lost the flicker.  This is below the wobble rpm, so wobble would make the sextant unuseable before flicker.  However, their must have been serious attenuation of the incoming starlight.  No doubt they kept their marine sextant onboard for the occasions when its use was possible.  DaveP

     

       
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