Join Date: Jan 2008
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If serious about celestial navigation you need to know the error in your timepiece, but what is more important than absolute accuracy is a consistency. A watch that gains 4 seconds a day is still fine if you have measured the error and if it is a consistent reproducible error.
A watch that gains some days, looses others, depending on temperature etc will be inaccurate for celestial navigation.
So the watch thatís closest after 2 weeks, even if it was spot on, may be still a poor choice, with poor consistency that happens to have evened out over the 2 weeks.
Checking it every day for 2 weeks would be a better test. The winner (for accurate celestial navigation) would be the watch with the most consistent result.
If looking at the imaginary worst case when the GPS system is wiped out (extremely unlikely IMHO) its worth remembering many things like a nuclear pulse that would wipe out the GPS system will also take out quartz watches. So a mechanical watch may be your best back up even if its inherently less accurate.