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    Sextant accuracy (was : Plumb-line horizon vs. geocentric horizon)
    From: Pierre Brial
    Date: 2005 Feb 11, 22:38 +0400

    Hi Frank,
    > Frank Reed a ?crit:
    > Pierre Brial, you wrote:
    > "Not yet. My sextant has a mechanical accuracy of 0.2', but despite
    > the
    > fact I have adjusted it, repeated tests on star distances show me that
    > it is difficult to have a practical accuracy of under 0.8'. But may be
    > this is also because of my lack of experience or inaccuracies in my
    > eye."
    > Do you have a good telescope on it? I have found that I can only get
    > down to 0.2' accuracy with a 7x35 monocular on my sextant.
    I think you got the point. I've got a 3.5x38 telescope. Recently I tried
    a lunar distance with Saturn. The ephemeris give for Saturn a semi
    diameter of 0.2', that is a whole diameter of 0.4'. But through the
    scope, I see only a spot. A bright one, but nevertheless a spot. So the
    magnification is too small to get a 0.4' accuracy.
    > "Are these [Bowditch] notes available somewhere ? Foreign accounts on Reunion for
    > 18th century are not well known here..."
    > It's in the Boston Public Library in Massachusetts. I have only read
    > summary accounts, but next time I'm out east, it's on my list of
    > things to read. I'll let you know if there's more of interest
    > regarding Reunion.
    I will be very grateful if you can find informations about this. Also
    let me know in case these note will be published.
    Best regards
    Pierre Brial

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