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Robert Eno wrote:
"For how much longer will  the US Government publish the Nautical Almanac?"

I think it's impossible  to say. It's not very expensive, so I would guess it
will be around for a while  longer. But let's suppose both the US Govt and
the UK govt decide to kill  funding for the nautical almanacs completely. What
happens next? The ephemeris  data for all of the objects we observe is already
available for the next few  centuries at a level of accuracy higher than that
required by celestial  navigation. The refraction tables, dip tables, etc. can
be re-calculated by  anyone who cares to do it. There is only one quantity
that needs to be  re-determined every few years: delta-T, that slowly changing
difference between  a true time standard (like atomic clocks) and the time
shown by the rotation of  the Earth. Fortunately, this quantity is of interest for
many constituencies  today so it's still watched closely and published
regularly. Even if it were  not, it is observable with ordinary sextant observations
as long as a  near-perfect time standard is available (the time on an average
cell phone is  accurate within a fraction of a second).

I would guess that if we wanted  to publish a commercial "Nautical Almanac"
with absolutely no support from  government sources (except the ephemeris data
which is alredy available on the  Internet today), we could have it up and
running and published in almost exactly  the same format as the current
government editions within six months.

And:
"will we eventually reach a point where the Nautical Almanac  will no longer
be available as a printed document - commercial or  government-produced --
but as a computer program with printable tables? I  sure hope not but it seems
to me that the world is fast going paperless and  electronic."

If you're willing to buy a paper almanac, then someone will  sell you one.
But how long are you going to be at sea? If you're going for two  weeks, perhaps
you would like pages printed specifically for those days instead  of the
entire year. Home-computer printing seems like a better option in that  case.

And:
"For that matter, will there still be a practical  requirement for
observatories to collect and calculate astronomical ephemeris  data. Certainly these
data will likely be maintained for astronomers but what  about for the mariner,
who requires a slightly different version?"

It's  all done. Apart from the delta-T issue, I could print for you today the
Nautical  Almanac for the year 2106, and it would be accurate to the nearest
arcsecond.  The numerical integrations are just that good. We could even print
it today with  simple instructions for determining delta-T at home with rules
for applying that  correction to the data as printed in 2006.

Anyone wanna buy the Nautical  Almanac for 2106 today? Cause I'll sell you
one... for the right  price...

-FER
42.0N 87.7W, or 41.4N  72.1W.
www.HistoricalAtlas.com/lunars

   

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