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    Re: Sextant Calibration
    From: John Rae
    Date: 2006 May 15, 16:11 -0700
    Just to add my two-bits worth to the discussion.
    Some time ago I obtained a second-hand MAC Japanese sextant.  Like many sextants, this instrument has both a separate adjustment knob and a micrometer drum on the same shaft.
    On first using this sextant, I found that when the drum micrometer wheel was set at zero, the index mark on the arm was about half-way between the degree marks on the arc.  This could easily cause a misreading error.   So by using the screwdriver adjustment on the micrometer screw/drum knob, I was able to adjust the micrometer drum to read zero when the arm markings were in alignment.  Then it was a time consuming but simple job to reset the mirrors so that the IC was acceptably small.
    The IC seems to stay at a stable reading, but I check it each time I use the sextant, an almost automatic task.
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