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    Re: Precision clock
    From: Fred Hebard
    Date: 2008 Jan 10, 15:51 -0500

    If you can go digital, stop watches run continuously.
    On Jan 10, 2008, at 1:30 PM, Geoffrey Kolbe wrote:
    > 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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