# NavList:

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

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
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
>
> 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:

Browse Files

Drop Files

### 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)