NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Accurate quartz watches
From: Peter Fogg
Date: 2005 Mar 19, 20:18 +1100
From: Peter Fogg
Date: 2005 Mar 19, 20:18 +1100
Keeping a log just records the raw data; it makes sense when plotted as a graph. I use the elapsed time (days, weeks, etc) on the horizontal axis, the seconds above/below zero (perfect time) on the vertical axis. If the rate is stable the graphed line rises/falls as a straight line. If the line bends or, worse, turns to the other direction, the rate is unstable. When the watch is reset the line begins again, ideally parallel to the old one. With 3 graphs (or more) to compare, the time can usually be calculated and accuracy checked to the nearest second, well into the future - as would be needed without external verification of correct time. The beauty of this simple system is that there is no need for rare, expensive and vulnerable timepieces. Almost any clock/watch can potentially be used, such as the pool of crew's watches; as a back up when other sources of correct time are unavailable. The authority, to return to my earlier posting, is not any of the watches, but the log (graph).