NavList:

Could there be a seasonal variation overlayed with and aging variation?

Just a curiousity question that occured to me based on other members mentioning temperature dependence.  No don't bother to pursue this more.

Regards,

Bob II

Re: Timekeeping in the post-WWV/post-HF world
From: Roger W. Sinnott
Date: 2018 Sep 26, 20:39 +0000

Robert:

Another graph in the article fits a straight line across all the data and exaggerates the ups and downs.  But they don't clearly indicate a seasonal variation.  The changes occur more leisurely, and I think they are related to aging of the crystal or the battery (or both).  

The fairly steady gaining rate of 50.4 seconds per year is what I found remarkable.  Deviations of up 7 seconds either way were measured with respect to this rate.  If a navigator determined the rate from a shorter interval (say, 1 year instead of 4), and extrapolated for a similarly short interval beyond that (1 year again), the deviations would be much less than 7 seconds.

In the article, I analyzed the time-keeping quality of this watch by the same method that was used 250 years ago to judge Harrison's No. 4 chronometer (as described by Rupert T. Gould in his classic, The Marine Chronometer) .  My $6 watch did considerably better than that chronometer.

Roger