Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Digital watches for use as a chronometer
    From: Gary LaPook
    Date: 2010 Sep 14, 17:35 -0700

      Here is the photo.
    
    gl
    
    On 9/14/2010 3:06 PM, Gary LaPook wrote:
    >  A year ago in September 2009 we discussed using cheap digital watches 
    > as chronometers in the thread "How many chronometers?" I described an 
    > experiment I was doing using three cheap ($17.00 each) watches to 
    > determine how useful they would be as a chronometer. ( I have provided 
    > links to some of my posts in that discussion below.)
    >
    > The experiment has continued now for almost a year and this is an 
    > update to the prior posts.
    >
    > Since I had modified the test conditions temporarily to see what 
    > effect very cold temperatures would have on the rates of the watches, 
    > I had to restart the experiment on September 18, 2009, 360 days ago. 
    > The three watches, "A", "B", and "C" were, respectively, 7, 31 and 60 
    > seconds fast at that point. I had computed their daily rates to be 
    > .1919, .3737 and .6263 seconds per day respectively. The watches are 
    > kept in a cabinet with a minimum-maximum thermometer (see photo) and 
    > the temperature range was 62.5° to 82.4° F ( 16.9° to 28.0 °C.)
    >
    > I have checked the watches on five occasions by comparing them with 
    > the radio time signal from WWV and estimated the time to the nearest 
    > half second. Using the daily rates, I predicted what the accumulated 
    > errors should be and compared them with the actual error and the 
    > difference would have been the error if relying on the predicted 
    > errors for navigation.
    >
    > The first occasion was on November 13, 2009, 56 days after the start. 
    > In the format for A, B, and C in seconds: actual error; predicted 
    > error; difference.
    >
    > A = 17.0/17.7/-.7:  B = 52.0/51.9/ .1:  C = 95.0/95.1/ -.1
    >
    > Averaging these differences equals -.2
    >
    >
    > December 31, 2009, 104 days:
    >
    > A = 26.5/27.0/ -.5:  B = 70.0/69.9/ .1:  C = 124.0/125.1/-1.1
    >
    > Averaging these differences equals -.5
    >
    > March 16, 2010, 179 days:
    >
    > A = 41.0/41.3/-.3:  B = 97.0/97.9/ -.9:  C = 172.5/ 172.1/ .4
    >
    > Averaging these differences equals -.3
    >
    > June 23, 2010, 278 days:
    >
    > A = 61.5/60.3/1.2:  B = 134.0/134.9/ -.9:  C = 232.0/234.1/ -2.1
    >
    > Averaging these differences equals -.6
    >
    > September 13, 2010:
    >
    > A = 79.0/76.1/2.9:  B = 164.0/165.5/ -1.5:  C = 281.0/285.5/ -3.5
    >
    > Averaging these differences equals -.7
    >
    > Evaluating this data shows that the greatest difference between 
    > predicted time and actual time was 3.5 seconds after 360 days which 
    > would result in less than one minute of longitude error in almost a 
    > year. So using any one of these watches as a chronometer would provide 
    > sufficient accuracy for celestial navigation.
    >
    > Averaging the three readings resulted in a maximum difference of .7 
    > seconds which would provide a longitude to an accuracy of less than 
    > one-quarter of a minute.
    >
    > So it appears that if the watches can be kept in the cabin where the 
    > temperature can be maintained at a comfortable temperature for the 
    > occupants, 17° to 28° C, that these three $17 watches are all you need 
    > for a year of voyaging without recourse to a radio time signal.
    >
    > gl
    >
    > Check out these previous posts:
    >
    >
    > http://www.fer3.com/arc/m2.aspx?i=109724&y=200909
    >
    > http://www.fer3.com/arc/m2.aspx?i=109757&y=200909
    >
    > http://www.fer3.com/arc/m2.aspx?i=109766&y=200909
    >
    > http://www.fer3.com/arc/m2.aspx?i=109824&y=200909
    >
    > http://www.fer3.com/arc/m2.aspx?i=109825&y=200909
    >
    > http://www.fer3.com/arc/m2.aspx?i=109847&y=200909
    >
    > http://www.fer3.com/arc/m2.aspx?i=109894&y=200909
    >
    > http://www.fer3.com/arc/m2.aspx?i=109942&y=200909
    >
    >
    >
    >
    
    
    
    
    

    File:


       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site