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    Re: Early days of noon-sights...
    From: Lu Abel
    Date: 1999 Jan 25, 12:29 EST

    I don't know all the answers to Russel's questions, but let me at least
    throw out a few comments on declination.
    >From what I understand, beyond pure dead reckoning, navigators up through
    about the mid-15th century had only Polaris sights as a source for latitude.
    As most who have even cursorily read of the 15th Century voyages of
    discovery, Prince Henry of Portugal (third son of the king, so not much to
    do except be available in case his two older brothers died) early in the
    century established the first scientific institute to study, advance, and
    teach navigation.  Some believe Columbus studied there at one point in his
    career.  The 15th Century equivalent of America's space program of the 1960s
    was Portugal's determination to get to the Orient by sailing around the
    bottom of Africa -- no mean feat, since at the beginning of the century
    European knowledge of the coast of Africa extended only about 50 miles south
    of the Mediterranean.  The Portugese pushed steadily southward over the
    century, finally passing the Cape of Good Hope at the end of it.  While
    there is no record of his actually been on a sea voyage, Henry the Navigator
    pushed his scientists to solve the practical problems of navigation needed
    for this exploration of Africa.
    One of the major results was the first table of Sun declinations, worked up
    by a couple of astronomers on Henry's staff about mid-century.  And it was
    none too soon, since the Portugese explorers were down to the equator and
    it's darn hard to see Polaris from south of it :-).  The declination tables
    allowed the Portugese navigators to determine latitude without Polaris, and
    allowed them to record and chart what they found south of the equator.
    One thing I don't know is how soon declination tables spread to other
    navigators -- navigational data (charts, sailing directions, and, I'm sure,
    declination tables) were considered state secrets back then.  I'll leave it
    for some Columbus experts to say whether he might have had them.
    Lu Abel
    > -----Original Message-----
    > From:	Russell Sher [SMTP:rsher{at}XXX.XXX]
    > Sent:	Thursday, January 21, 1999 10:14 PM
    > To:	'navigation{at}XXX.XXX'
    > Subject:	[Nml] Early days of noon-sights...
    >
    > I am curious to know; In the early days of parallel sailing and relying
    > almost exclusively on the noon-sight, Where did early navigators obtain a
    > table of declinations? Was this perpetual or was it renewed annually?
    >
    > Russell
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