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    Re: Early lunars
    From: George Huxtable
    Date: 2010 Mar 22, 00:02 -0000

    
    Sorry; last time I sent this, I missed sending the attachments. Second 
    attempt-
    
    ========================
    
    Wolfgang , under threadnames "Sobel and longitude", and "Early lunars", has
    provided useful information about Columbus and his attempts to determine
    his position in Jamaica.
    
    I've riffled through my own shelves, and rather to my surprise have
    discovered six books dealing with Columbus. A surprise because I'm no fan
    of Columbus. He was an incompetent navigator. And he  has a lot to answer
    for.
    
    The eclipse, of the Moon,  happened on 29 Feb 1504, on Columbus' fourth
    voyage, when he was marooned in Jamaica. Columbus tells us how he used the
    predicted event to impress the native Indians with his powers.
    
    One volume, "The voyages of Christpher Columbus", by Cecil Janes (1930)
    doesn't mention the event at all.
    
    Another, "Columbus in the age of discovery", by Zvi Dor-Ner (1992), seems
    to be more about the author and his TV productions than about Columbus. He
    states that Columbus took his eclipse data from a Nuremberg Almanac, and
    pictures the entry about eclipses, which I attach, from Regiomontanus'
    Calendarium.
    
    Bjorn Landstrom's "Columbus", 1966, derides the longitude derived by
    Columbus from the eclipse, which, as he says, would have placed him way out
    in the Pacific, but approves of the latitude observation, which we will
    consider.
    
    "The life of the Admiral Christopher Columbus, by his son Ferdinand",
    (trans. Keen 1960) deals only with the impressing-the-natives story, as
    does Alexander McKee, in "A World too Vast" (1990), though there he states
    that the eclipse prediction came from Abraham Zacuto.
    
    The only real meat, then, is provided in Morison's "Admiral of the Ocean
    Sea", of 1942, and I attach the relevant page for  Columbus' words to be
    assessed. On another page, Morison tells us that the eclipse prediction was
    from Regiomontanus' Ephemerides, "printed at Nuremberg before the end of
    the century, but containing predictions for 30 years ahead". I have
    attached what Morison wrote about the finding of longitude and latitude
    (when marooned at Santa Gloria, taken to be St Ann's Bay, roughly in the
    middle of the North coast of Jamaica).
    
    Can anyone make any sense of the way Columbus deduced that the ending of
    the eclipse "when the moon had just returned to its light" (whatever that
    may mean, in terms of the phase of the eclipse), two hours and a half after
    sunset, implied a longitude difference of seven hours and fifteen minutes
    from Cadiz, whereas that difference is more like four hours and forty
    minutes. Wolfgang has suggested that Columbus hadn't realised that the
    prediction was given for Nuremberg, but even that would imply a longitude
    difference of less than six hours.
    
    As for the latitude, what Columbus tells us is inadequate. In that era,
    Polaris was best part of 4 degrees from the Pole, and so it was vital to
    allow for it, done by looking at the position of the Guards, a pair of
    pointer stars, with respect to a mythical figure, usually that of a naked
    man, standing upright in the Pole sky with Polaris at his navel. (For
    understandable reasons, many navigators from Latin lands preferred to see
    the figure of a naked woman).
    
    All Columbus tells us is that "the Guards were on the arm", without telling
    us which arm. And it's important. David Waters, in "The art of
    navigation..." (1958) quotes "Regimento do astrolabio e do quadrante",
    dated 1509? as saying "When the Guards are on the West Arm the North Star
    stands above the Pole one degree and a half", and presumably vice versa
    when the Guards are on the East Arm. Columbus doesn't say which, though we
    could easily check for ourselves in a planisphere program, and check the
    eclipse details too: I haven't done so. Any refraction corrections in
    altitude are negligible in view of the low accuracy of Columbus'
    observations.
    
    Morison has simply compared latitude with altitude, and found them to be
    half-a-degree apart, without (apparently) allowing for Polaris, and deduced
    that Columbus could observe to half a degree. Morison may have been a good
    historian, but not a navigator.
    
    George.
    
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ----- Original Message ----- 
    From: "Wolfgang Köberer" 
    To: 
    Sent: Saturday, March 20, 2010 2:47 PM
    Subject: [NavList] AW: Re: AW: Early lunars
    
    
    According to Maddison ("Medieval scientific instruments and the development
    of navigational instruments in the XVth and XVIth centuries", 30) the
    nocturnal was first described by Ramón Llull by the end of the XIIIth
    century, but this is based on an edition of 1721 and I would not place too
    much faith in it.
    Hester Higton ("Sundials at Greenwich", 387) also states that nocturnals
    were in use "by at least the tenth century"; she does not give any
    reference, though.
    Finally Günther Oestmann has written an article in the SIS-Bulletin (No.
    69,
    5 - 9) on the history of the nocturnal and says that there must have been
    forerunners of the instrument that early and that - in contrast to the
    astrolabe - manuscripts on this type of instrument are rare; only 18
    manuscripts describing the use and manufacture from the 15th and 16th
    century are known to him.
    
    Wolfgang
    
    
    
    
    
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ----- Original Message ----- 
    From: "George Huxtable" 
    To: 
    Sent: Sunday, March 21, 2010 10:19 AM
    Subject: Re: [NavList] AW: Re: AW: Early lunars
    
    
    | Wolfgang , under threadnames "Sobel and longitude", and "Early lunars", 
    has
    | provided useful information about Columbus and his attempts to determine
    | his position in Jamaica.
    |
    | I've riffled through my own shelves, and rather to my surprise have
    | discovered six books dealing with Columbus. A surprise because I'm no fan
    | of Columbus. He was an incompetent navigator. And he  has a lot to answer
    | for.
    |
    | The eclipse, of the Moon,  happened on 29 Feb 1504, on Columbus' fourth
    | voyage, when he was marooned in Jamaica. Columbus tells us how he used 
    the
    | predicted event to impress the native Indians with his powers.
    |
    | One volume, "The voyages of Christpher Columbus", by Cecil Janes (1930)
    | doesn't mention the event at all.
    |
    | Another, "Columbus in the age of discovery", by Zvi Dor-Ner (1992), seems
    | to be more about the author and his TV productions than about Columbus. 
    He
    | states that Columbus took his eclipse data from a Nuremberg Almanac, and
    | pictures the entry about eclipses, which I attach, from Regiomontanus'
    | Calendarium.
    |
    | Bjorn Landstrom's "Columbus", 1966, derides the longitude derived by
    | Columbus from the eclipse, which, as he says, would have placed him way 
    out
    | in the Pacific, but approves of the latitude observation, which we will
    | consider.
    |
    | "The life of the Admiral Christopher Columbus, by his son Ferdinand",
    | (trans. Keen 1960) deals only with the impressing-the-natives story, as
    | does Alexander McKee, in "A World too Vast" (1990), though there he 
    states
    | that the eclipse prediction came from Abraham Zacuto.
    |
    | The only real meat, then, is provided in Morison's "Admiral of the Ocean
    | Sea", of 1942, and I attach the relevant page for  Columbus' words to be
    | assessed. On another page, Morison tells us that the eclipse prediction 
    was
    | from Regiomontanus' Ephemerides, "printed at Nuremberg before the end of
    | the century, but containing predictions for 30 years ahead". I have
    | attached what Morison wrote about the finding of longitude and latitude
    | (when marooned at Santa Gloria, taken to be St Ann's Bay, roughly in the
    | middle of the North coast of Jamaica).
    |
    | Can anyone make any sense of the way Columbus deduced that the ending of
    | the eclipse "when the moon had just returned to its light" (whatever that
    | may mean, in terms of the phase of the eclipse), two hours and a half 
    after
    | sunset, implied a longitude difference of seven hours and fifteen minutes
    | from Cadiz, whereas that difference is more like four hours and forty
    | minutes. Wolfgang has suggested that Columbus hadn't realised that the
    | prediction was given for Nuremberg, but even that would imply a longitude
    | difference of less than six hours.
    |
    | As for the latitude, what Columbus tells us is inadequate. In that era,
    | Polaris was best part of 4 degrees from the Pole, and so it was vital to
    | allow for it, done by looking at the position of the Guards, a pair of
    | pointer stars, with respect to a mythical figure, usually that of a naked
    | man, standing upright in the Pole sky with Polaris at his navel. (For
    | understandable reasons, many navigators from Latin lands preferred to see
    | the figure of a naked woman).
    |
    | All Columbus tells us is that "the Guards were on the arm", without 
    telling
    | us which arm. And it's important. David Waters, in "The art of
    | navigation..." (1958) quotes "Regimento do astrolabio e do quadrante",
    | dated 1509? as saying "When the Guards are on the West Arm the North Star
    | stands above the Pole one degree and a half", and presumably vice versa
    | when the Guards are on the East Arm. Columbus doesn't say which, though 
    we
    | could easily check for ourselves in a planisphere program, and check the
    | eclipse details too: I haven't done so. Any refraction corrections in
    | altitude are negligible in view of the low accuracy of Columbus'
    | observations.
    |
    | Morison has simply compared latitude with altitude, and found them to be
    | half-a-degree apart, without (apparently) allowing for Polaris, and 
    deduced
    | that Columbus could observe to half a degree. Morison may have been a 
    good
    | historian, but not a navigator.
    |
    | George.
    |
    | contact George Huxtable, at  george@hux.me.uk
    | or at +44 1865 820222 (from UK, 01865 820222)
    | or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    | ----- Original Message ----- 
    | From: "Wolfgang Köberer" 
    | To: 
    | Sent: Saturday, March 20, 2010 2:47 PM
    | Subject: [NavList] AW: Re: AW: Early lunars
    |
    |
    | According to Maddison ("Medieval scientific instruments and the 
    development
    | of navigational instruments in the XVth and XVIth centuries", 30) the
    | nocturnal was first described by Ramón Llull by the end of the XIIIth
    | century, but this is based on an edition of 1721 and I would not place 
    too
    | much faith in it.
    | Hester Higton ("Sundials at Greenwich", 387) also states that nocturnals
    | were in use "by at least the tenth century"; she does not give any
    | reference, though.
    | Finally Günther Oestmann has written an article in the SIS-Bulletin (No.
    | 69,
    | 5 - 9) on the history of the nocturnal and says that there must have been
    | forerunners of the instrument that early and that - in contrast to the
    | astrolabe - manuscripts on this type of instrument are rare; only 18
    | manuscripts describing the use and manufacture from the 15th and 16th
    | century are known to him.
    |
    | Wolfgang
    |
    |
    |
    |
    | 
    
    
    
    
    

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