A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Murray Peake
Date: 2018 Sep 25, 23:49 -0700
On the subject of high-accuracy watches, I bought a Longines VHP 1000 Oe Quartz watch a few years ago (secondhand online) , and when I checked this morning it was 32 seconds slow - it's at least 4 years since I set it, so it is within spec.
A very cheap option available until recently was the Texas Instruments eZ30 Development Tool which is a bit of circuitry TI packaged as a sports watch with the interesting features that it has a wifi interface and programming capability. Out of the box accuracy was poor - mine drifted 15 seconds or so a day. However there was a project which I followed and implemented where a third party programmed the Version 3 HAQ-ezChronos firmware which allowed the watch to be calibrated at a number of temperatures, a parabola fitted to the quartz frequency against temperature, and the watch display adjusted to compensate. Setting was by wifi from a PC with recently set internet time. I did a rough compensation and the accuracy was very acceptable. Mechanically the watch was a bit primitive (it was just a development kit) and mine didn't survive a battery change. Interesting idea though.