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    Re: Sextant Collimation Error
    From: David Pike
    Date: 2020 Jun 25, 09:34 -0700
    Greg
    Do you know how big that collimation error is when using a ghost ring
    and not looking through it straight?
    Bill
    
    Bill.   I wondered about this, because 6th Form Physics says that a marine sextant ought to be tilt proof in the fore and aft direction.  Newton says the measured
    angle must be twice the angle between the mirrors; full stop.
    
    However, we rock the sextant to find the vertical.  Perhaps a better place to begin an analysis ought to be looking at a plan view of the situation. 
    Might there be a similarity between looking from the left of ring to right of horizon mirror as opposed to looking down the centre of and not holding the sextant vertical? I’m off
    to try it.  DaveP
       
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