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Leap seconds correct for variations (mostly the slowing down) in the
rate of the Earth's rotation.  I think everything else that's an input
to the Nautical Almanac tabulations -- the Earth's orbit around the
sun, and also the other planets, the Moon's orbit around the earth,
proper motion of the stars, etc. -- is computed from the free-running
time that ignores leap seconds.  In a way, we're still clinging to the
pardigm used in the Almanac's early days, when things were tabulated
by Greenwich Apparent Time.  Fortunately for navigation, and for
Geoffrey's long-term almanac, most celestial objects don't move very
much in a few seconds.  Thus, for practical navigation, it doesn't
matter whether we use UTC or the free-running clock for their
positions.  It *does* matter when we go to translate those positions
into GHA.

To answer the question that started the thread, I think future
navigators will compute a position, then adjust their longitude.  That
uses (marginally) better positions for the celestial objects than the
alternative, which would apply a sort of "equation of time" before
looking up positions.

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