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    Chronometer rate (was Re: Endeavour Voyage Recreation)
    From: Steven Wepster
    Date: 2001 Jul 13, 6:31 AM

    > >How were they
    > >measuring 9 seconds a day error in the clock in the South Seas - what would
    > >have been their reference; I suppose averaged from total difference from
    > >Lunar measurements ?
    >
    > I'm posting the answer on-list in case anyone else is puzzled. Here goes-
    >
    > It's really quite simple. Not from on board, though. But having made a
    > landing, set up some sort of instrument to look along a South-North
    > direction. It doesn't need to be aligned at all accurately, though. An
    > astronomical quadrant or a pillar sextant would do the job. Set its
    > altitude to that of some bright star and wait for the moment when that star
    > passes the cross-wires, recording the time reading on the clock you want to
    > calibrate. Leave the instrument undisturbed and record the next crossing in
    > the same way, one sidereal day later, 23 hours 56 minutes 4.1 seconds. If
    > the time interval measured by the clock differs from that amount, that's
    > the daily error in the clock.
    >
    Dear George,
    
    That is indeed a simple way to check the chronometer rate (as long as
    nobody kicks yourinstrument..). Was this indeed the method used in the
    period?
    
    _Steven.
    

       
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