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    Nomograms and emergency navigation
    From: James R. Van Zandt
    Date: 2007 Oct 15, 07:54 -0400

    
    I've always had my doubts about the actual practicality of a lifeboat
    sextant (i.e. that they were intended mostly to impress the
    passengers) - since CN would also require a cronometer, an almanac,
    and a calculator or sight reduction tables.  If the ship's officers
    were bringing those to the lifeboat, then why not bring a good sextant
    too?
    
    However, with the sextant alone one could still determine latitude.
    
    A few weeks ago, Andrew Nikitin posted some nomograms for altitude
    correction, with the suggestion they could be attached to the sextant
    itself.  I suggest one additional nomogram, for reduction of a Polaris
    sighting.  I envision a star chart of the polar region, surrounded by
    a circular scale, with instructions something like this:
    
      "Rotate the figure to match the sky, then read the correction from
      the scale directly under Polaris."
    
    I also suggest the offset of Polaris from the north pole in the chart
    be exaggerated, so the navigator can confirm the sign of the correction
    for himself.  I would also include a worked example.
    
                    - Jim Van Zandt
    
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