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    Re: Historical charts and mapping
    From: John D. Howard
    Date: 2016 Aug 19, 14:26 -0700

     David,

    From my readings over the years on observatories I think time could be measured to that precision.   Clocks were avaible to a accuracy of 1/100 second at that time and the famous Riefler regulator clock came out just a little later in 1890.

    The clock could not display time to that precision but the telescope could.  A micrometer eyepiece was used with several wires in view and a star's passage over each of the several wires could be recorded to the millisecond.  If I rember correctly the obsever would hit a button to record the exact moment.

    Surveyors and especially astrometors could measure angles very precise - down to 1/10 second arc in the 1880's

    Now, down near the antipod I don't know.   :-)

    John H.

       
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