NavList:

   

Reply

Back in 1767, the "Nautical Almanac" was launched. Today, I can visit a
bookstore (most likely online) and buy the "Nautical Almanac". But it would
be misleading to draw a straight line between those two books. Yes, they're
in the same lineage, but there are a few side-branches on the family tree.

I use the expression "mariner's almanac" to refer to an almanac intended to
be used primarily at sea. If an almanac is intended primarily for land-based
astronomers and surveyors, I call it an "astronomer's almanac". In the
history of the almanacs, very often these two almanacs were combined into
one publication. At other times, when the volumes became too bulky, they
were spun off into separate publications. All too often, the names of the
almanacs did not necessarily match their function.

The German almanacs were separated right from the beginning. The Nautisches
Jahrbuch was (and is) the mariner's almanac. It was never intended to supply
information useful only on land, such as ephemerides of the asteroids.

The British almanac, the "Nautical Almanac and Astronomical Ephemeris", was
a combined almanac from 1767 through the late 19th century. Through 1833 it
was primarily a mariner's almanac with less attention to the needs of
astronomers (and by 1820, the astronomers were complaining loudly about it).
Following a major revision in 1834, the almanac became more noticeably an
astronomer's almanac, including detailed ephemerides of minor planets, but
the information for mariners was also significantly enhanced (for example,
lunar distance tables from 1834 included planetary lunars and also
pre-calculated values of "P.L. Diff" which slightly shortened the
interpolation process). From 1896, the first section of the NA&AE was
published separately for the convenience of mariners. It was an extract,
designed to save weight and money.

The Spanish nautical almanac was first issued in 1792 and generally followed
the British model. The name from 1855 was simply "Almanaqie Nautico". It
served both mariners and astronomers. An extract for mariners only did not
appear until early in the 20th century (1912).

The French "Connaissance des Temps" (various spellings earlier) was also a
combined almanac supposedly intended for mariners and astronomers, however
it was very much a technical document from an early date, much more useful
to astronomers. Just a year ahead of the British almanac, the French added
planetary lunar distances in 1833. Starting in 1889, as the C. des Temps
continued to grow in size, the French began publishing the "Extrait" later
known as the "Ephemerides Nauiques". This was a slim volume containing only
navigationally useful information. It was a mariner's almanac. It's worth
noting that the lunar distance tables included in the 'extract' were
considerably shortened since it was widely acknowledged that almost no one
used lunars at sea after the middle of the 19th century.

The American almanac (the home-developed version rather than simple reprints
of the British version) was first published in 1852 with data for 1855 (N.B.
when looking at almanac history dates, you often have to check whether the
quoted date is the publication date or the ephemeris date). It was named the
"American Ephemeris and Nautical Almanac" and it served both mariners and
astronomers. Within at most three years, a smaller subset of this book was
published separately for mariners and known as the "American Nautical
Almanac" (N.B. this was the usual 'spine title' though the title on the
front cover changed a few times over the years). Through the early part of
the 20th century, the American Nautical Almanac was merely the first half of
the complete almanac. It did not contain any unique information. Publishing
it separately was simply a means of saving a little money. This example, as
already mentioned, was followed by the French and British over 30 years
later.

At the beginning of the twentieth century, the various almanac publishing
authorities modernized the mariners' almanacs by deleting obsolete material
and adding new formats and data sets more useful to modern navigators.

 From 1905, the lunar distance tables were dropped from the French
"Connaissance des Temps" as well as the mariner's "Extrait". Two years
later, they were dropped from the British almanacs (last year that included
them was the almanac for 1906). However, it's worth noting that the British
Nautical Almanac as well as the mariner's extract (soon to be known as the
"Abriged Nautical Almanac") included an appendix for calculating these
distances as well as a method for clearing them (related to Airy's method)
through 1919 in the main almanac and 1924 in the mariner's abridged almanac.
Just so we're clear, these dates tell us nothing about the longevity of
lunar distance observations which were long obsolete. They tell us something
about the history of the almanacs and no more.

[The German mariner's almanac, the "Nautisches Jahrbuch", included lunar
distance tables through 1919 and possibly a few years after that. I haven't
pinned down a date]

On the American side of the ocean, the lunar distance tables were dropped
after 1911 (the volume for 1912 had no LD tables), but a detailed appendix,
annually updated showed how to calculate them from other almanac data if
desired.  This appendix was included through 1933 in the mariner's almanac
and through 1935 in the astronomer's almanac (which has always been more
conservative).

(to be continued in part II)

 -FER
www.HistoricalAtlas.com/lunars
PS: for the wiki-folk, the citations for all of this material would be the
documents themselves, e.g. "American Nautical Almanac for 1912".



--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---

   

Reply