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    Finding longitude in the 16th century
    From: Alexandre Eremenko
    Date: 2012 Sep 1, 12:55 -0400

    De Veer's account of Barentsz expedition is available on the web,
    but the English version is very poorly scanned (this applies to many
    old books). It is hardly readable, and not searchable.
    So I quote here for the NavList a part relevant to the
    longitude. I find this very interesting, as a rare recorded example of XVI
    century Cel Nav.
    Notice that Barentsz died during the expedition and his
    original astronomical records
    are probably not available. At least they are not available to me.
    De Veer who left a nice description of the expedition was a
    ship's carpenter, btw. I am quoting from the Russian translation.
    I am enormously impressed with a Dutch carpenter's education in XVI
    Begin quote:
    ...Decided to turn to the "Ephemerides" by Joseph Scala, printed in Venice,
    and containing the data for 1589-1600.
    We found here that on January 24 (when we saw the Sun for the first time),
    there was a conjunction of the Moon and Jupiter,
    in Venice at 1 hour of night.
    So we all made a careful investigation, when
    this conjunction
    hapened near our house, where we lived. We found that on the same
    24-th of January, when in Venice the said conjunction happened at 1 a.m.,
    here it was about the time when the Sun was in the East.
    By continuously observing the two said planets we found that slowly they become
    closer and closer, until finaly they stood exactly one above another;
    both planets were in the constellation of Taurus,
    and this was at 6 in the morning. When Moon and Jupiter vere over our house
    in conjuncton, they beared NtO (NbE in English), but the S of the compass
    was really SSW. The Moon was 8 days old. From this we see that the Moon and Sun
    were at 8 rhumbs (15 points-A.E.) distance. This happened at about 6 a.m.;
    our place is 5 hours of longitude from Venice, and counting every
    hour 15d, it turns out that we were 75d to the East of Venice.
    We can conclude that we found our true longitude. Indeed, the longitude of
    Venice is 37d25' and latitude is 45d5' from which follows that our place
    the Novaia Zemlia had longitude 112d25' and latitude 76d.
    (Russian editor's remark: The longitude of Venice is 12d21' E of
    Greenwich, Barentsz determination gives 87d21' in the modern count).
    It is known that the difference in longitude between the very East point of
    Novaia Zemlia and Gabin cap, the East end of Tataria, where the shore turns to
    South is 60d, but one should take into account that the degrees are not
    as large here as on the equator...
    End quote.
    This is preceded by a long discussion of the phenomenon wich is now called
    "Novaia Zemlia effect". The first sunrise after the Polar night occured
    11 days earlier than they expected. The sunrize was spotted by de Veer
    himself. Then he says:
    Begin quote:
    Our capitan and I, and one more preson went to the sea shore on the South
    end of Novaia Zemlia, where against our expectation, I (I was the first)
    saw the edge of the Sun. We immediately returned to tell this grat news
    to Barentsz and to the rest of our camarades. Wilhelm Barentsz, a wise and
    experienced navigator, did not want to believe this message, saying that
    the Sun cannot rise earlier than in 11 days, on this latitude, on his
    approximate count. But we insisted that we saw the Sun.
    There was a lot of arguments.
    On 25 and 26 of January it was foggy and dark and nothing could be seen.
    So those who were not believing us thought that they won.
    However on the 27, in a clear weather we all saw a whole disc of the Sun
    above the horizon. It was absolutely clear to everyone that we saw it on
    the 24.
    A lot of opinions was expressed on this, namely that this contradicts all
    ancient and new writers and even to the law of nature and to sphericity
    of the Earth and heavens. Some even stated that we saw the daylight in our
    dreams, but this was not so...
    We asked each other whether we could make a mistake in days reconning...
    But this was impossible because we carefully marked every day using our
    clock, and when the clock was frozen, using the sandglass...
    We also used all other tools to keep correct time reconning...
    End quote.
    Nowadays the phenomenon is explained as an abnormal refraction,
    of course.
    P.S. There is a nice Dutch movie about this expedition, "Nova Zembla".

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