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    Re: Accuracy and sources of time
    From: Tom Sult
    Date: 2011 Sep 19, 08:08 -0500
    Do any of you use these automatic update clocks with a radio receiver. I just got one and am playing with it. I assume the basic uncorrected time piece is not that great. But it is "obsessive" and updates often. 

    Thomas A. Sult, MD
    Sent from iPhone

    On Sep 19, 2011, at 6:27, Apache Runner <apacherunner@gmail.com> wrote:

    NIST time - typically good to a couple of tenths.   Probably once a month.   

    I also have a spread sheet where I check the drift of the watch, so if I'm separated from NIST, I can make a correction.

    I'd say that any more than once a month would be 'obsessive' - although I could probably go longer if I had to.

    4 seconds = 1 arc second in the most extreme case, and a month seems about right for my drift.

    On Mon, Sep 19, 2011 at 1:25 AM, Frank Reed <FrankReed@historicalatlas.com> wrote:

    For all of you practical navigators as well as all of you not-so-practical navigation enthusiasts, what's your favorite source for time? A web site? A GPS device? A radio time signal? When you set or check a watch, how accurately do you worry about setting from any of these sources: one second, a fraction of a second? And when a good watch has been set, how often do you feel the need to double-check it? The obvious answer is "as often as possible" but consider two cases: when you have easy access to a time signal update, how often would you prefer to update (or put differently, what sort of updating frequency would be pointless or even obsessive), and for the other side of the coin, when you have no access, how long would you feel comfortable going without an update or double-check? We've talked before about trusting inexpensive watches for months or even as much as a year in an experimental situation. What's the longest you would really trust one in practice?


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