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    Re: Nautical Almanac Symposium of 1999
    From: Courtney Thomas
    Date: 2005 Feb 13, 16:56 -0500

    With what intent is the publication of "Computer Programs for Sun and
    Moon Illuminance with Contingent Tables and Diagrams" ?
    
    Thank you,
    Courtney Thomas
    
    
    
    Paul Hirose wrote:
    
    > 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 19th century, completely superseded lunar distances."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
    >
    >
    
    
    --
    s/v Mutiny
    Rhodes Bounty II
    lying Oriental, NC
    WDB5619
    
    
    

       
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