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    Re: Time and cel nav, a stupid question
    From: Paul Hirose
    Date: 2008 Apr 26, 12:47 -0700

    Lu Abel wrote:
    > I've found cheap Timex or equivalent
    > quartz watches to be remarkably good timekeepers (at least on my wrist,
    > I've never taken them off and subjected them to freeze-boil cycles) --
    > if given the chance to measure watch rate, I'd be pretty confident of
    > going for a month or even more without cross-checking with WWV or
    > equivalent.
    Here are the daily rates of my $25 Timex Expedition for the last year. I
    actually check it only once per month, and convert the error to the
    equivalent daily rate for that month.
    +.43 March 2007
    +.41 April
    +.41 May
    +.40 June
    +.35 July
    +.34 August
    +.40 September
    +.45 October
    +.44 November
    +.43 December
    +.42 January 2008
    +.42 February
    +.45 March
    This watch was bought in 2000. The original battery is still installed,
    though for about a year it's been so weak that the display goes blank
    when I press the illumination button. The watch still keeps good time,
    so I haven't bothered to get the battery changed.
    There seems to be a remarkably consistent relationship between seasonal
    temperature changes and watch rate. In the table above, the fastest
    rates are +.45 in October 2007 and March 2008. The corresponding values
    a year before were +.43 and +.43. The slowest rates are +.35 and +.34 in
    July and August, compared to +.26 and +.35 a year before. That +.26 is
    not a typo. However, it may be significant that the anomalous value
    occured when I forgot to do my monthly check until the middle of the
    month. So "June" had 6 weeks and "July" had 2 weeks. I may have made a
    mistake in my math. The consistent values from May and September tend to
    confirm that suspicion. The respective rates were +.39 vs. +.41, and
    +.40 vs. +.40, for 2006 vs. 2007.
    For the correct time, I call WWV and the USNO on my Nextel cell phone.
    The delay is about 1/4 second compared to WWV on shortwave radio. It's
    so  consistent that I make no correction for the delay. I used to tune
    WWV on the shortwave radio for my time reference, but sometimes the
    propagation was bad on all frequencies. It's less trouble to use a phone.
    I block messages that contain attachments or HTML.
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