Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding

Compose Your Message

Add Images & Files
    Re: Bowditch Long Term Almanac Tables
    From: Gordon Talge
    Date: 2002 Oct 23, 15:53 -0700

    Dan Allen wrote:
    > One of the nice features of the Bowditch volumes from 1958 until 1984
    > is Appendix H:
    >      Long Term Almanac
    > It made carrying along a Bowditch (or two from 1975 until 1984)
    > self-contained: it
    > had the theory and the tables needed to do "lifeboat" navigation.  Now
    > of course
    > this useful table has been removed with no replacement in later
    > editions.  How sad.
    > (These editions also had H.O. 211 as Table 35, "The Ageton Method",
    > also now deleted.)
    > The Appendix had two pages for the Sun's GHA and Dec for 10 different
    > dates per month,
    > for each month of the year.  There are corrections based upon year so
    > that the maximum
    > error for altitude would not exceed 2.0' of arc.  It also has
    > information for 38
    > navigational stars in a compact little table with promised errors of
    > less than 1.3'
    > of arc, as well as a table of the GHA of Aries, along with 2 auxiliary
    > tables.  The
    > whole thing with explanation takes up about 5 pages.  Very neat.
    > Question: does anyone know the source of this table?  Is it just
    > Newcomb's formulas
    > put into a table?  (Newcomb's formulas were the basis of the Nautical
    > Almanac before
    > computers and DE405.)
    > Question #2: could we come up with a newer, better, more compact long
    > term almanac
    > ourselves?  Just a thought.
    > Dan
    In vol 3 of Pub NO 249 ( The old HO 249 ) "Sight Reduction Tables for
    Air Navigation" there is a very good "Sun Table" starting on page 342.
    The theory is that "what goes around, comes around every 4 years" sorta,
    with the appropriate corrections. The table is for 1981 to 2016. so
    it has 14 more years.
    The stars are pretty regular too. The moon is way to "weird" for a
    long term table.
    A few years ago, using DE200/LE200 and Chebyshev Polynomial
    I was able to duplicate the polynomials in the now defunct "Almanac for
    Computers" for the Sun, Moon, and Planets. This information in a some
    different form is still available in offical form from the British,
    last time I checked.
    -- Gordon
                                 (. .)
    | Gordon Talge WB6YKK               e-mail: gtalge{at}pe.net    |
    | Department of Mathematics       http://www.lbusd.k12.ca.us |
    | Wilson High School                  Long Beach, CA         |
    | (o-    Debian / GNU / Linux                                |
    | //\    The Choice of the GNU Generation                    |
    | v_/_                  .oooO                                |
    |    - E Aho Laula -     (  )   Oooo. - Wider is Better -    |
    +-------------------------\ (---(  )-------------------------+
                               \_)  ) /

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site