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    Re: Quartz Watch Movement Replacement
    From: Bill B
    Date: 2012 Jun 18, 20:00 -0400

    On 6/18/2012 6:53 PM, Greg Rudzinski wrote:
    > To time to the tenth of a second is best done directly with the
    > shortwave and split/stopwatch. There is a fractional delay when using
    > non video still camera images. The camera clock is only + 0.5 seconds
    > precision or so where the stopwatch is good to a hundredth of a second.
    > Your video technique should be good to 3/100 of a second if everything
    > is synchronized.
    
    Greg
    
    The way I figure it at 30 fps the increments are 1/30 or 0.033 seconds.
      I did check the frame rate against a stop watch.
    
    Perhaps we are on different pages or my explanation was lacking.  I am
    not using the camera clock at all. I simply place the two displays side
    by side and video about 5 seconds worth.  Then I can playback advancing
    (or backing up) frame by frame.  For example if I am using the NIST
    computer display as a standard I can watch it change over to a new
    second and then count how many frames it takes a slow watch's display to
    catch up. 5 frames is 5/30 or 0.17 seconds slow.
    
    As to trusting my eye vs reflex time and/or sound ticks vs sight, I do
    not have that much faith in myself.  NIST claims about 0.2 second is the
    best we  can distinguish. Based on my results I believe that.  I was
    rather amazed that it could take up to 5 frames for my RCC's large
    digits to completely change the second in certain combinations! I cannot
    see it, but the camera does. If my eyes were better that would make a
    strong case for an analog display.
    
    The most disappointing results were from my Garmin 76. In an article
    Garmin engineers stated that Garmins run 1/2 to 1 second slow as the
    chip spends the majority of its energy on the position/time computations
    rather than the time display.  They also stated 1 to 2 seconds delay for
    Lowrance, and did not mention Magellan etc.
    
    In my observations the Garmin would actually advance 2 seconds at a time
    with a weak signal; skipping the intermediate second completely.  Even
    with strong horizon-to-horizon satellite views it would often "stack"
    seconds--a quick change from one to the next then a relatively long
    delay before the next change over. I have not yet been able to discern
    if the average time lag from UTC is constant/predictable.
    
    As for my RCC that was the subject of so much supposition after Alex and
    I observed together, it has been put through every torture test I can
    devise without destroying it, is viewed approximately 40 times daily,
    and has never so much as hiccuped.  It is spot on after its 2 AM EDT
    reset.  My only problem with it is a 0.9 second drift (slow) over the 24
    hours between resets. Voluntary standards would have it within
    plus/minus 0.5 seconds of UTC at any time.  Fortunately the drift rate
    is constant, so easy to mentally adjust to UT1--until the June 30 leap
    second ;-)
    
    Bill B
    
    
    
    

       
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