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    Re: Precision clock
    From: Geoffrey Kolbe
    Date: 2008 Jan 10, 18:30 +0000

    Thankyou for this Paul. I was hoping to get away from using essentially two
    clocks - a chronometer (WWV in your case) and what amounts to a deck watch
    (the stop watch).
    Stop watches usually have a maximum period over which they will run as a
    stop watch - usually about ten hours or so. So it is not possible to start
    a common stop watch at the top of the hour at midnight and let it run on
    for months more.
    Geoffrey Kolbe
    >Years ago when I computed satellite orbital elements from visual
    >observations, I obtained UTC from from a digital stopwatch. I started at
    >a known time by listening to WWV on a radio. Rather than the top of a
    >minute, I started the watch on the 10th second of the minute. This
    >allowed me to catch the rhythm of the seconds ticks, and hit the button
    >at the instant of the tick, rather than reacting to the tick. (WWV omits
    >the ticks at the 29th and 59th seconds, which makes this method harder
    >to use at the top or bottom of a minute.)
    >After starting the watch, I would then test for an accurate setting by
    >hitting the "split" button (to temporarily freeze the display while the
    >watch continued to run) on several ticks, checking for a near zero
    >fractional seconds reading each time. With a bit of practice it's no
    >great trick to hit the mark plus or minus .02 second.
    >To time satellite observations, I used the split button and let the
    >stopwatch memory save the times. It could hold up to 10, which was more
    >than I ever needed.
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