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Paul Hirose posted a forwarded message about some almanac history:

Throughout the 1930s, the British Nautical Almanac included detailed explanations, and by the end of that decade each volume was almost 1000 pages. Although the explanations were of value to many astronomers, much of this information was unnecessary to the daily user of the publication, and there were complaints regarding the books being unwieldy. Cutting the size of the yearly almanac by providing a more permanent explanatory supplement was under consideration at Her Majesty’s Nautical Almanac Office (HMNAO) when World War II began. At that time, “a drastic cut was imposed on the overall size of subsequent editions by the exigencies of war” (Nautical Almanac Offices of UK and USA 1961). The preface to the 1942 almanac describes separating the ephemeral material from the permanent data and explanations, and also states, “It is possible that publication of the Supplement will be delayed for some time.” In fact, it did not get published for 20 more years.

This may confuse some celestial navigation enthusiasts. The problem here is that the Nautical Almanac in that period was not the Nautical Almanac in the modern sense. The volume known worldwide as the Nautical Almanac in the first half of the twentieth century was, in fact, closest to what is known today as the Astronomical Almanac. That huge tome, over a thousand pages as described above, was not at all the resource used by celestial navigators. Instead it was a volume of exceedingly precise astronomical data on all the planets (including Uranus, Neptune, and eventually the former planet Pluto) as well as positional data on asteroids, stars, and other objects. It was a volume used by astronomers in observatories. 

When it was first published in 1767, the Nautical Almanac & Astronomical Ephemeris was aimed at one specific market: lunarian navigators. Its tables facilitated the determination of longitude by lunar distances. Other astronomical tables for the Sun's declination and the positions of the planets had limited value to navigators. Navigators already had excellent tables of the Sun's position, and the planetary data was largely useless for navigation. Almost immediately the Nautical Almanac came to be known by its shorter name, and almost immediately it became a priceless resource for astronomers even more than navigators. By the middle of the nineteenth century, the Nautical Almanac primarily targeted the astronomical community with celestial navigators along for the ride. Navigators at sea no longer required lunar tables which fell into disuse in the first half of the nineteenth century (before c. 1825 on British vessels, c. 1850 on American vessels), and basic tables of the Sun's declination and the equation of time were almost the only ephemeris data required by a navigator traversing the world's oceans. Meanwhile astronomers consumed data. The Nautical Almanac ballooned in size as tables for dozens of asteroids (originally counted as principal planets) were included in the volume. In addition all of the tables were published with far greater precision than what was required for celestial navigation.

Starting late in the nineteenth century private publishers (first) and soon the government almanac offices began producing "extracts" or "abridged" versions of the rapidly expanding principal almanacs. And this pattern wasn't unique to the British almanacs. In the USA the "American Ephemeris & Nautical Almanac" began life as a volume intended to satisfy both astronomers and navigators, but that publication soon split into two branches as well. In Spain the Almanaque Nautico likewise grew into a large volume aimed at astronomers while an 'extracto' was published for ocean-going navigators. In France the "Ephemerides Nautiques" tables were published for navigators while the "Connaissance des Temps" was reserved for astronomers. In all of these navigation cultures, the astronomers' almanac had originated as the navigators' almanac and was usually historically associated with ocean navigation. Astronomical almanacs carried nautical associations and names.

By the 1930s --the period described in the quotation that Paul Hirose posted above-- there were two distinct almanacs in most navigation cultures. In Britain there was the "Nautical Almanac" which was a massive volume aimed at astronomers in observatories, and published alongside it was a slim, "cheap" volume known as the "Abridged Nautical Almanac". That's what navigators used, if they purchased a government almanac at all (pricate almanacs like Brown's Nautical Almanac were very popular). In the USA, the "American Ephemeris & Nautical Almanac" was a large volume, finely published and handsomely bound, again targeting astronomers, and in parallel there was a small paperback volume called the "American Nautical Almanac". Both of these had begun as simple extracts, collecting the nautically useful pages from their heftier siblings, but by the 1930s the connection between them was fading rapidly, especially with the introduction of "GHA" and other data designed to facilitate the "New Navigation". At this point in history we have the extraordinary situation where the "Nautical Almanac" was not nautical at all! I have to wonder how many naive navigators showed up at their first celestial navigation class in 1935 toting a heavy copy of the "Nautical Almanac", and how many other potential navigators were intimidated by the tables found in that volume. How many of them did not realize that the "Nautical Almanac" was not the "nautical almanac"?

During the Second World War and accelerating postwar, the almanac offices in Britain and the US began to consolidate their production of these "ephemeral" tables and eventually they intended to unite them in common volumes and rationalize the confused titles of the publications. In 1958 the radically revised modern Nautical Almanac, jointly published by the almanac offices of Britain and the USA, appeared in nearly its final form, though for a couple of years the old names were retained: the "American Nautical Almanac" in the US and the "Abridged Nautical Almanac" in Britain. The astronomical volumes were merged and finally in 1981 the historical names were dropped on the astronomers' almanac replaced by the simple and apt title "Astronomical Almanac". And incidentally the almanac offices in other countries followed suit. In 1961 the Spanish "Almanaque Nautico" became the "Efemerides Astronomicas" while the smaller extract "para uso de los navegantes" became, sensibly, the "Almanaque Nautico".

Finally, the quotation at the top refers to a publication that was spun off from the "Nautical Almanac". This was the volume today known as the "Explanatory Supplement". And again, this was not relevant to celestial navigators. It was a reference work for astronomers in observatories.

Frank Reed
Conanicut Island USA

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