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    S.I.R.S. sextant calibration sheet
    From: Andreas Gwilt
    Date: 2022 Jul 28, 12:08 -0700

    Hello all,

    this is my first time actually writing anything after almost a year of lurking -- I have a lovely Admiralty Patt 491 sextant with a rather overwhelming calibration sheet issued by S.I.R.S. Navigation Ltd. in 2004, the summary of which is in the attachment. I'll just list all my questions:

    1. Am I right in thinking that Error is the number to look at, and Diff. is probably just the difference to the (nonexistent) previous calibration sheet?

    2. If so, do I want to add or subtract the Error values from my reading?

    3. Does the Tol: +- 72" really mean a tolerance of over a minute for that measurement, in which case isn't the whole thing rather useless?

    Andreas Gwilt


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