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    Octant calibration
    From: Paul Hirose
    Date: 2000 Sep 17, 12:34 AM

    Bill Murdoch,
    
    I'm glad my message gave you some ideas. There may be some problems
    with your plan, though. If your octant has a telescope, it might be
    difficult to focus at across-the-garage range to carry out your
    calibration procedure.
    
    Also, centering the index arm pivot at the center of your measuring
    tape circle would be critical, I think. If it's off, you'd get a
    parallax error. The setup I described for the Mark 3 is not sensitive
    this way because the "star" is a generated in a collimator. I.e., the
    rays from the collimator shining on the index mirror are a parallel
    bundle, so imperfect centering on the rotary table doesn't affect the
    apparent direction of arrival. Centering only needs to be good enough
    to assure good illumination as the table rotates to different
    positions.
    

       
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