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    Re: Sextant experiment
    From: Peter Monta
    Date: 2021 Jun 13, 09:38 -0400
    Hi Modris,

    My sextant SNO-M shows constant difference between these two average index corections.

    How much difference are you seeing?  Can you see it by placing the two solar images in contact, then slowly rolling the sextant 180 degrees (without touching the micrometer assembly)?  A difference of, say, 0.3' or larger would be visible this way, but smaller differences would need multiple trials as you describe.

    I don't have a good guess as to how much flexing might be expected from a metal frame, or whether the flexing couples more into side error than into the main angle.  Still, if you're seeing more than a few arcseconds of difference, it might be from something actually flopping around (which could be subtle, e.g. play in the index bearing) rather than from ordinary elastic flexure.

    It strikes me that sextant calibration, when it was done at all, would have been done horizontally.


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