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    Re: The development of bubble sextants
    From: Douglas Denny
    Date: 2009 Aug 18, 04:56 -0700

    Agreed. Brain not in gear.
    Coriolis is relevant when own local inertial frame is moving relative to moving Earth's inertial frame.
    I am too sloppy in my fast writing of these things without thinking.
    PIM is affected by rotating Earth inertail frame relative to the "fixed" gyro 
    axis and suitable restoring feedback.
    All this is getting too esoteric and far far away from the point I made 
    however - that horizontal accelerations cannot be eliminated unless there is 
    some time-integrating reference to the local geopotential force.
    That is exactly what the clockwork averaging mechanism does on the MkIX BM 
    sextant; or in a more crude fashion, with the median averaging method on some 
    WW2 bubble sextants.
    It is also exactly what is done with the early type of air-operated artificial horizons in aircraft.
    Douglas Denny.
    Chichester. England.
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