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    Re: How Many Chronometers?
    From: Robert Eno
    Date: 2009 May 06, 17:13 -0400

    I'd like to chime in here (no pun intended)
    
    The methods described by the group seem to be dependant upon taking 
    observations with relatively course nautical instruments. Seems to me unless 
    you are one hell of a superb navigator, you would not be able to discern what 
    is a clock error vs. what is an observation error. Determining your longitude 
    and/or time via lunar distances for example, is only as accurate as the 
    observer and his sextant and with so many variables (temperature, observer 
    error, instrument error, refraction etc.) is it realistic for one to expect 
    that he can determine chronometer error by this means? Unless your 
    chronometer is out by hours.
    
    I may be way off base here so feel free to correct me.
    
    Robert 
    
    ----- Original Message -----
    From: Brad Morris 
    Date: Wednesday, May 6, 2009 4:57 pm
    Subject: [NavList 8164] Re: How Many Chronometers?
    
    > 
    > Hi Jim
    > 
    > True, it is a clock with a known rate, but the rate can change! 
    > Let us assume for a moment a mechanical chronometer.  As the 
    > lubrication ages, the rate changes.  In the literature, you can 
    > see instances of a sea rate and a land rate.  Temperature can also 
    > affect the rate.  For an electronic (quartz) chronometer, a very 
    > run down battery will have a slowing rate.
    > 
    > For any of these items, how would you know the rate was changing?  
    > Greg suggested comparison to other chronometers.  Henry and I have 
    > suggested celestial observations with a known longitude.
    > 
    > We can even see Worsley and Shackleton, attempting to correct 
    > their chronometers by lunar occultations, when stuck on the ice in 
    > the Weddell Sea.
    > 
    > Best Regards
    > Brad
    > 
    > 
    > -----Original Message-----
    > From: NavList@fer3.com [NavList@fer3.com] On 
    > Behalf Of James N Wilson
    > Sent: Wednesday, May 06, 2009 4:39 PM
    > To: NavList@fer3.com
    > Subject: [NavList 8163] Re: How Many Chronometers?
    > 
    > 
    > Brad:
    > 
    > I guess I thought that a chronometer was defined as a clock with a
    > constant rate of change.
    > 
    > Jim Wilson
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