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    Re: Navigation without Leap Seconds
    From: Lu Abel
    Date: 2008 Apr 18, 09:03 -0700

    frankreed@HistoricalAtlas.net wrote:
    > And Lu wrote:
    > "And that last sentence is the key to your question of "how would I
    > practice celestial navigation if we didn't have leap seconds"   As long
    > as I could convert my local time into Almanac time, it wouldn't matter,
    > just as I adjust from local time to GMT."
    >
    > So you also agree that it would be no issue, right? The author of the time
    > article suggested that the "vanishing breed" of celestial navigators would
    > be upset over the abolition of leap seconds. I think that's incorrect.
    Oh, I absolutely agree it would be no issue.  As I said in my original
    post, there's a difference between the passage of time (as measured,
    say, by an atomic clock) and answering the question "what time is it?"
    If we lived in a world without leap seconds, our chronometers would show
    leap-second-less time and the almanac would show the positions of
    celestial bodies in leap-second-less time.  As long as we all agree on
    how to answer the question "what time is it," it really doesn't matter
    exactly how we do it.  An extreme example would be to suddenly start
    keeping metric time - metric watches and metric almanacs, what's the big
    deal?
    > We
    > would have little problem adjusting the rules in a world without
    > leapseconds. But I'm still interested in some of the options as to how this
    > might be done. Suppose I publish a nautical almanac today for the year 2058.
    > How could I use it correctly for celestial navigation in that year? Adjust
    > the input time??
    Publishing a Nautical Almanac today for 2058 would face the issue of
    trying to predict how many leap-seconds would be inserted into UTC in
    the next 50 years.   I can predict the location of the celestial bodies
    quite well, but I can't predict whether UTC will be different from
    today's time by three or five or 10 seconds.   Maybe would I need to add
    another line to my time calculations in my sight reduction forms; in
    addition to Watch Error and ZD, I need a line for "leap second
    corrections."   Either that or the government publishes 50 years worth
    of Nautical Almanacs at once ("we got a good price on a big order") and
    therefore declares the end of leap-seconds so as to not obsolete this
    huge inventory :-P .
    
    Lu
    
    
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