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    Re: Dropping leap seconds and the impact on celestial navigation
    From: Geoffrey Kolbe
    Date: 2011 Sep 10, 09:10 +0100

    Even today in celestial navigation, to be strictly accurate about
    time, one should really factor in the DUT correction to "broadcast
    time" or UTC, to get UT1, which is time system to which the Nautical
    Almanac is referenced. By the interpolation of leap seconds into UTC,
    DUT is currently kept to less than 0.9 seconds, so the maximum error
    will be about a quarter of a mile if this correction is not made.
    This is usually neither here nor there when using a sextant to fix a
    position at sea, so it is not usually accounted for, but for more
    precise celestial fixes it does become a significant error.
    Does it matter that DUT grows to be larger than one second? I can
    hardly think that it does.
    Will DUT be a difficult number to get hold of? It isn't now, I don't
    see why it should be in the future. You would only really have to
    acquaint oneself with the value of DUT once a year to maintain an
    accuracy in time of one second.
    Does the Nautical Almanac have to publish its data with reference to
    UT1? Given today's computer power, it should be a trivial matter to
    use broadcast time - or any other time system - as the time reference
    system for its data. An equivalent of DUT could be available in the
    form of a time correction to keep the ephemerides accurate to their
    specified precision. Then, for all practical purposes, the status quo
    would be maintained for practitioners of celestial navigation.
    I think it is obvious that we need to keep to a sun based time system
    so that the working day continues to be during daylight hours. But I
    see no reason why it should not be a leap hour once a century or so
    rather than a leap second once a year or so. After all, "summer time"
    comes and goes each year without the sky falling down about our heads.
    Geoffrey Kolbe

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