Yuo can find a better picture on
http://de.wikipedia.org/wiki/
Bild:Braunschweiger_Dom_kleine_Sonnnenuhr.JPG
Willy LEENDERS
Hasselt in Flanders (Belgium)
www.wijzerweb.be
Op 23-aug-08, om 19:35 heeft Roger Bailey het volgende geschreven:
Google quickly finds pictures and information on the Braunschweig
Cathedral
sundial.
http://commons.wikimedia.org/wiki/
Image:Braunschweig,_Dom_St._Blasii_mit_Sonnenuhr.jpg
The pictures show a dial with the words Anno 1716 across the top.
A text reference identifies "Hans Geog Hartel" with the sundial is
1659.
http://historydb.adlerplanetarium.org/signatures/edit.pl?edit_id=6954
Is there an earlier sundial dating back to 1346 with the same
characteristics, polar gnomon and equal hours?
Can any of you scan Carl Roslund's BSS article and email me a copy?
Regards, Roger
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: "Frank.King" <[EMAIL PROTECTED]>
Cc: "sundial" <[EMAIL PROTECTED]>
Sent: Saturday, August 23, 2008 8:54 AM
Subject: Re: equal and unequal hours
Dear Frank, Maes and other friends,
The question about the introduction of use of the polar gnomon is
old.
Actually, are very few the informations about this. Rohr wrote in
his book
that the polar gnomon was introduced in Europe with the Crusaders
returning from the arabian country. I also think that the polar
gnomon was
re-invented in Europe from the Arabian astronomical science.
Sure the mechanical tower clock with the equal hours was a good
reason for
the use of polar gnomon in the equal hours sundials, but I have
some dubt
about the importance of this "only one" reason.
It is true that the first mechanical clocks was on the towers
around the
begin of the 1300. And the first vertical sundials with the polar
gnomon
was done arond the first half of 1300.
The interesting articles of Curt Roslund in the BSS Bulletin,
september
2005, pag. 116-119, show the vertical sundial of Braunschweig
Cathedral of
1346 with the equal hour lines and a polar gnomon.
A have find recently a important gnomonical manuscript attribuited
to the
end of 1300 with drawings of horizontal and vertical (also east
and west
plane) sundials with the equal hours line. But this is a new topic
for a
my next articles.
Hence, we have the sources that the equal hours line on the
horizontal and
vertical sundials with an probable polar gnomon was used in the
Europe at
the end of 1300.
Thanks for attention and the best wishes to all
Nicola Severino
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