NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Chronometer rate (was Re: Endeavour Voyage Recreation)
From: Steven Wepster
Date: 2001 Jul 13, 6:31 AM
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.