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    Re: The 57 Navigational Stars (and Zuben'ubi)
    From: Frank Reed CT
    Date: 2005 Apr 27, 02:26 EDT
    A couple of additional bits of history trivia on the Navigational Stars:
     
    Before 1916 navigators were expected to pick their stars for sights from long lists of hundreds of stars comparable to the list of stars towards the back of the modern "Nautical Almanac". The "Selected Stars" list began in 1916 with the first publication of the "American Nautical Almanac" (the title existed previously but the volume for 1916 was the first one that was as a separately prepared and edited publication; it had formerly been an unmodified extract of the increasingly astronomy-oriented "American Ephemeris and Nautical Almanac"). Its purpose was essentially the same as today's list --it gave navigators a relatively short list of bright stars to choose from with good coverage across the whole celestial sphere. The list originally had 55 stars. They were numbered as they are today but occasionally the order changed since precession slowly changed the right ascensions of the stars. For example, in the 1920s, Achernar and Polaris switched places on the list. If this standard of keeping the list in correct order by right ascension (reverse order by SHA) were still in place, Kochab and Zubenelgenubi should have swapped places recently, but today the numbers are considered permanent. By the way, this early origin for the star list also explains why the list is organized seemingly backwards. Modern navigators use SHA which runs in the opposite direction from right ascension. But back in 1916, they still used right ascension and so the almanac listed and numbered the stars in that order. The numbered list of Selected Stars does not seem to have been particularly important to navigators until the 1940s and 50s.
     
    The list of 55 stars gets bumped up to 57 stars in 1950 by the addition of El Nath and Alkaid. Why? Maybe because the British almanacs typically listed 59 stars, so they split the difference. The British almanac's list of stars was not numbered and changed seasonally. For example, Spica would not be listed on the monthly star list when it was too close to the Sun to observe. Or perhaps the number was increased to 57 simply because there was more room on th page. A change in page size occurred at about this time. This would match Herbert's suggestion.
     
    The big revision of the navigational star list in 1953 that we've already discussed swapped out six stars in the "American Nautical Almanac" list and replaced them with others mostly in the southern sky. There were various spelling and name changes. I've been able to confirm that in this year the list of 57 navigational stars in the "American Nautical Almanac" was also published in the British 'Abridged Nautical Almanac' (as with the American almanacs, this was the almanac actually used by mariners while the publication commonly known as "The Nautical Almanac" in the first half of the 20th century was the astronomers' almanac). And it's worth noting that the name Alkaid would have come into common usage among British navigators at this time. So there's one answer to the question that started all of this: Benetnasch became Alkaid in 1953.
     
    By the way, in the early years of the star list, Rasalhague was spelled with an 'h'. Later by 1944 at least, the 'h' had been dropped only to be restored when the list took its final form in 1953. And Alnilam was known as Alnitam in the "American Nautical Almanac" before the 1950s.
     
    -FER
    42.0N 87.7W, or 41.4N 72.1W.
    www.HistoricalAtlas.com/lunars
       
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