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    Re: Accuracy and sources of time
    From: Greg Rudzinski
    Date: 2011 Sep 19, 10:10 -0700

    Back in my ship watch standing days I would set or check my digital Seiko wrist watch by short wave time tick or by the doppler sat nav clock prior to every celestial observation. The ship had a Seiko analog quartz chronometer in a box which was rated once per week but was never relied on as long as a short wave signal was available. Today aboard my ketch I use a Grundig S350 short wave time tick or a Seiko Atomic dual time zone travel clock to set a Timex reef gear digital wrist watch. A direct reading of the wrist watch is then taken with one second subtracted to allow for the time it takes to bring the eye from the scope to the watch. For more precise timing I have also been using a digital stop watch which is started on the minute of a short wave time tick. When both the short wave radio and the atomic clock are not receiving signals there is aboard a pair of rated quartz analog wrist watches. By knowing the rate of each watch I am able to determine the number of weeks since the last set and thus the correction to apply to each watch. If I had only my best rated quartz analog watch available for use then it would easily provide accurate time to within plus or minus 4 seconds for up to a year. Using time within 4 seconds of UT is good enough but I like to be within plus or minus a second if possible.

    Greg Rudzinski
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