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    Re: Almanac data in 1855 (British vs American)
    From: Frank Reed CT
    Date: 2005 May 16, 23:25 EDT

    Gordon T, you wrote:
    "It would seem to me  that by 1855, having the correct time via
    accurate chronometers was not  really much of an issue, if you
    could afford a good one. I think that doing  Lunar Distances at sea
    was not that common."
    
    That's true. The 1850s  were the closing days in the use of lunars at sea.
    There were many nautical  astronomy experts on-shore who advocated them, but in
    practice, by this date,  they were rare. Why was that? I brought this issue up
    because PART of the reason  was the inaccuracy of the almanac data.
    
    And:
    "They may have been done  on land or in port for getting time in
    isolated places"
    
    Lunars were  used at sea as a check on the longitude on a fairly regular
    basis from the  origin of the Nautical Almanac through the 1850s. In the period up
    to about  1835, they were a check on the dead reackoning longitude. In the
    period from  about 1835 to about 1855, they were a check on the chronometer
    longitude. As  I've written before on the list, they were never (or only rarely)
    considered a  "primary" means of getting longitude. There was no "lunars era"
    before the  "chronometer era", no period when navigators did lunars every day
    in the same  way that they used chronometers in later years. But this should
    not be taken to  mean that lunars were some unwieldy exotic thing never
    practiced by real men at  sea. Far from it. There is ample evidence in the logbooks
    that have survived  from the period. Many ordinary navigators practiced lunars
    and checked their  longitudes with them on a fairly regular basis. For lunars,
    this "regular basis"  meant several times a month. This is hard data. We don't
    have to speculate  because the navigators wrote it all down.
    
    And wrote:
    "but I think the  Noon Sun Sight ruled, and maybe
    still does. It is the easiest to do, and  requires the least
    calculations."
    
    The noon sun sight is and was  irrelevant to the issue of lunars since lunars
    were sights for determining  longitude. With a chronometer, and a graphed set
    of sights around LAN, you can  get longitude (with some important caveats)
    but without a chronometer, the Noon  sight is useless for longitude.
    
    And:
    "I don't think that 30 seconds  difference would be that big of
    a deal between the British and American  Almanacs"
    
    Actually it was a HUGE deal, and the release of the American  almanac spurred
    the Europeans to improve theirs.
    
    You wrote:
    "LD's  seem to me to be very hard to do right and accurate, especially on
    board a  ship."
    
    You've been exposed to the mythology that developed during the  long death of
    lunars from the 1850s through the early 20th century. You should  really try
    some lunars, and find out for yourself whether they're difficult.  They're
    challenging, yes, but not really much more difficult than any accurate  celestial
    sight. Despite the moaning and groaning from many modern would-be  historians
    of lunars, these observations did not require three observers, they  did not
    require four hours to clear, and they did not require expert knowledge  of
    nautical astronomy. Ordinary navigators regularly determined their longitudes  to
    the nearest half degree or so. They did it with ten or twenty minutes of
    observation and about twenty minutes of math work, and yes, they did it at  sea.
    
    And you noted in a ps:
    "The British, and rightly so, complained  bitterly about us
    "up starts" ripping them off, with copyright violations. We  copied
    without regard, by reprinting tons of British
    books and documents.  It was kind of a sore in their side."
    
    That was true fifty years earlier  but not by 1855. The American almanac,
    when it was released in 1852 (with data  for the year 1855) was the best in the
    world.
    
    And:
    "The British Navy,  in spite of America's victories in Revolutionary War
    and in the War of 1812,  was still the best in the world and we knew it."
    
    Very true, but navies  are only one side of maritime history. The American
    commercial fleet in the  mid-19th century was enormous. By the 1840s, the
    eastern Pacific Ocean was  virtually an American lake. But not because of the US
    Navy --rather because of  the American whaling fleet. Hawaii is a US state today,
    and not an offspring of  the British Empire, because of this history.
    
    -FER
    42.0N 87.7W, or  41.4N 72.1W.
    www.HistoricalAtlas.com/lunars
    
    
    

       
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