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While browsing at a library, I came across the Proceedings of the U.S.
Nautical Almanac Office Sesquicentennial Symposium in 1999. Excerpts
from some of the presentations:

A History of the American Nautical Almanac Office

"Changes made to the Almanac during Eichelberger's years were mostly
technical or stylistic, but interesting landmarks nonetheless. One of
the most noticeable was the discontinuation of the lunar distance
tables beginning in the Nautical Almanac for 1912. Inquiries made in
1907 by the Chief of the Bureau of Equipment, showed that 'these
tables are practically no longer used by the navigators either of the
naval service or of the merchant marine.' Thus the chronometer method,
which had become the primary method of navigation already by the late
19th century, completely superseded lunar distances."


A History of the British Nautical Almanac Office

"I used to see the correspondence between Sadler and Clemence about
the unification of the [US and UK] almanacs for marine navigation. My
recollection is that it was Clemence [in the US] who proposed using a
layout with data for three days at each opening, but Sadler did much
to fill in the detail of the layout that was eventually adopted. In
this case, we produced the daily pages using an IBM card-controlled
typewriter and pre-printed ruled forms, which required the development
of a special, but simple, technique to ensure that the columns of
figures kept a constant distance from the rules."


Wallace Eckert, Computers, and the Nautical Almanac Office

"He recalls: 'They had no automatic equipment. Every digit was written
by hand and read and written repeatedly ..... They didn't have a
machine that would print figures automatically.' Eckert was then
[1940] 37 years eld, and he stayed for a little over four years. It
was clearly the most important period of his life. He felt that he had
done his most valuable work at the Nautical Almanac Office, and the
most important achievement there was obviously the Air Almanac...
Eckert's great merit, as well as his pride and joy for the rest of his
life, was that the intervention of human hands was almost completely
eliminated in the production and printing of this data. No error has
ever been reported."


Navy, A View from the Deckplates

"The traditional method of sight reduction using The Nautical Almanac
and sight reduction tables (Publication H.O. 229), takes about ninety
minutes to do the approximately 120 calculation steps to solve for six
star lines of position. These same calculations using The Nautical
Almanac and a programmed navigation calculator take about 45 minutes.

"In all, a navigator doing the calculations with the publications
spends about seven hours per day taking celestial observations and
performing the calculations. Using a navigation calculator the time is
reduced to about four hours per day."


Celestial Navigation by U.S. Civilian Mariners Near the End of the
Second Millennium A.D.

"The primary use of celestial navigation aboard large merchant ships
seems to be as a seldom-used backup to GPS. This situation does not
appear to be likely to change in the near future. Yet each ship
continues to carry equipment and tables to allow celestial navigation
should it be needed. One supplier of sextants arranged for a direct
shipment from the factory to a ship in Singapore to meet a
time-critical need. He was apologetic to the buyer, and recommeded
checking them upon arrival.

"'Don't worry,' came the reply, 'they'll probably never take the
sextants out of the boxes.'

"The attitude is quite different aboard yachts on long passages..."


New Technoligy for Celestial Navigation

"If celestial navigation is to assume a broader role in the modern
Navy's high-tech environment, its limitations will have to be
addressed: low accuracy (a few miles), limited time window for
observations (horizon must be visible), and low data rate. The sparse
amount of celestial data collected over the course of a day results
from the use of a human (with other duties) as a detector and
computer, the small number of target objects (usually just the Sun and
bright stars), and restrictions on the sky area used (altitudes 15 to
65 degrees). It turns out that all of these limitations are a
consequence of the way in which celestial navigation is now carried
out, rather than being fundamental to the technique. They are a result
of the human-intensive observing and computing procedure that we use,
and in that sense are self-imposed. However, if we are willing to
think a bit more broadly about how celestial navigation could be
performed, we find that these problems have technical solutions. In
fact, as we shall see, most of the needed solutions are available off
the shelf.

"Significant improvement to celestial navigation's accuracy and
availability will require changes in both the observational hardware
and the computional procedure used to obtain a fix. Let us look at the
mathematical situation first."


The Future of Almanac Data in the United Kingdom

"The fact is that an almanac office is simply expected to BE THERE,
ready to predict the phases of the Moon and times of sunrise and
sunset, to rule on whether the Sun was in a position to dazzle a
driver, and to say how long before dawn a military target will be
visible. But defence agencies may be reluctant to fund activities they
see as mainly civilian, and no one government department is likely to
accept that it should be responsible for supplying all types of
almanac information to anyone who requests it. Furthermore, the staff
who know how to do these things -- from first principles, without
having to ask anyone else, and always getting the right answer -- are,
in many cases, engaged in dynamical and positional astronomy research.
Unfortunately, for many decades now, astronomy has been the poor
relation to astrophysics when it comes to bidding for research grants.

"In recent years, these pressures have been compounded by rapidly
changing technology. Personal computers are now perfectly capable of
calculating everything in the Almanac -- with the right software. Many
individuals and companies can predict Sun, Moon and planet positions.
The public expects everything to be free, on the Web. And GPS has
swept all before it to become the primary method of navigation at
sea."


The Future of Almanac Data in the United States

"In my opinion, both the advantages of computer-based tools and
concerns involving over-reliance on technology are valid issues that
must be addressed in any plan for the future of the navigational
almanacs. Thus, we have proposed that the U.S. Navy fully approve and
promote STELLA for routine use in celestial navigation. We also
propose that a manual means of sight planning and reduction be
retained, but relegated to a backup role. If this policy is adopted,
USNO will likely produce an 'Abridged Nautical Almanac' specfically
for Navy use. This book will be published every three to five years
(to be determined) without the hourly tabular data for the Moon and
planets. Discussions with fleet navigators indicate that the Moon and
planets are often avoided, due to additional complexities in reducing
their observations. Of course, STELLA handles these complexities
automatically, and STELLA has the capability to generate lunar and
planetary almanac data in standard Nautical Almanac format on demand.
HMNAO would continue to produce the current Nautical Almanac and
ensure its availability in the U.S.

"It is important to note that this plan is only a proposal at this
time.

"The future of the U.S. Air Almanac is uncertain. Without a doubt, use
of celestial navigation aboard U.S. military aircraft is in rapid
decline. New aircraft, replacing existing aircraft, are being built
without sextant ports. GPS and inertial navigation systems are
becoming dominant. Reflecting this situation, there has been a major
reduction in celestial navigation training for military air
navigators. 'Undergraduate' training has essentially been eliminated,
and 'post-graduate' training has been reduced to a computer-based
course. Furthermore, we have been unable to identify any specific U.S.
Navy or Air Force requirements for continued publication of the Air
Almanac. The AA Department undertook a survey of users of The Air
Almanac in 1998. The survey results are still being analyzed, but
preliminary results indicate that there currently is a need for the
book. Furthermore, it appears that there will be at least several
types of military aircraft that will use celestial navigation for the
foreseeable future. Additional study is needed to understand the
requirements. Howover, it is quite possible that the U.S. Air Almanac
will be reduced in scope or terminated within the next five to ten
years.

"USNO has offered to produce for the U.S. military a version of STELLA
specfically designed for air navigation, but so far there has been no
formal interest."


This book is for sale by the USNO. They only accept orders the old
fashioned way, via the postal system. On the other hand, a 424 page
hardbound book for $10 is a good deal.

http://aa.usno.navy.mil/publications/docs/usnopubs.html

   

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