Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    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.
    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

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site