Re: Gnomon filaris mystery

2015-11-29 Thread Dan-George Uza 
One more interesting titbit regarding filar gnomons: in 1968 Romanian-born
German-language poet Paul Celan published the poem "Fadensonnen" which you
can listen to at the link below as read aloud by its author:

https://www.youtube.com/watch?v=tV_7AVKyBpo

The English translation of "Threadsuns" goes like this:

*Threadsuns*
*over the grayblack wasteness.*
*A tree-*
*high thought*
*strikes the light-tone: there are*
*still songs to sing beyond*
*humankind*

Some literary critics think that the word "Fadensonne" is an old synonym
for "filar gnomon", certainly making this one of the strangest sundial
poems I've come across.

Dan Uza


On Sun, Nov 29, 2015 at 7:55 PM, Dan-George Uza 
wrote:

> Hello,
>
> Catholic bishop Batthyany Ignac established one of the first astronomical
> observatories of Transylvania in Alba Iulia in the late 1700s, with
> Antonius Martonfi - a former Jesuit - serving as astronomer and director.
> The latter published a 400 page book in 1798 entitled "Initia astronomica"
> which lists the observatory's available technical equipments. Among them
> were two scientific gnomons, one of which is said to have been filar
> (gnomon filaris, gnomon filair, meridienne filaire). Today Martonfi's book
> is rather difficult to come by, there once was a copy in Cluj University
> library, but that has since vanished (perhaps it was stolen and sold off to
> collectors). So far I have been unable to gain access inside the
> Observatory in Alba Iulia and actually see what remains of these gnomons,
> but I managed to obtain a photo showing what appears to be a trap door on
> the wooden floor of the observing room, presumably with a cable running
> underneath up to the wall in the back, ending with a suspended weight (see
> enclosed). I've done some research and it seems this kind of sundial was
> first described by German physicist Christian Gottlieb Kratzenstein in
> 1782. A detailed description and drawing are also available in the work
> "Beschreibung der meteorologischen Instrumente" by Augustin Stark, a copy
> of which can be read here:
> http://www.e-rara.ch/zut/content/titleinfo/6013342
>
> Have a look at the drawing on the left of Tab. V on page 100. There light
> enters through a 2 mm hole drilled in a metal plate which is fixed outside
> the southern window, parallel to the equator, and the meridian cable runs
> across the roof of the room and also ends in a weight. From it you had to
> suspend one or more vertical wires, the shadows of which caught on a piece
> of paper were used to time solar transits. But contrary to the filar gnomon
> presented in this book, the meridian cable from the old observatory in Alba
> Iulia appears to run UNDER the floor so I am unsure how it was used. The
> question also arises whether there still are any similar working filar
> gnomons left in other old astronomical observatories.
>
> Dan Uza
>



-- 
Dan-George Uza
http://cerculdestele.blogspot.com
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Re: Gnomon filaris mystery

2015-11-29 Thread Roger Bailey 
Hi Dan,

This looks like the meridian sundial in the astronomy tower of the Clementinum 
in Prague. It is one of about 17 interesting sundials at the Clementinum. See 
http://www.waymarking.com/waymarks/WM86NC_Meridian_Sundial_in_the_Clementunum_Astronomical_Tower_Prague.

Here is my description of the sundial from that waymark. There are several 
photos with the waymark of this "gnomon filaris", a single wire acting as a 
shadow sharpener.

"When you visit the Clementinum in Prague, take the tour of the Astronomical 
Tower. Most do this to enjoy the view over the city but there is an interesting 
if subtle feature in the tower. A small hole in the south facing window at the 
top of the tower projects a bright spot onto a meridian strip on the floor and 
north wall of the room. This strip just below the prominent quadrant with a 
transit telescope is in a long wooden box with protective doors. This meridian 
is marked for the position of the solar spot at noon at different dates and 
solar declinations throughout the year. Just above the meridian strip is a taut 
wire carefully aligned north in the vertical and horizontal axes. 

When the solar spot projected onto the meridian strip is bisected by the wire 
shadow, it is solar noon. Then a flag was waved out of the window to signal to 
the gunners in the castle across the river. They then fired the noon cannon to 
mark Prague Noon. This procedure was established in 1842 and continued until 
1926 although Prague switched to Central European Time in 1912."

Regards, Roger Bailey

aka "arby101ca"

From: Dan-George Uza 
Sent: Sunday, November 29, 2015 9:55 AM
To: sundial@uni-koeln.de 
Subject: Gnomon filaris mystery


Hello,


Catholic bishop Batthyany Ignac established one of the first astronomical 
observatories of Transylvania in Alba Iulia in the late 1700s, with Antonius 
Martonfi - a former Jesuit - serving as astronomer and director. The latter 
published a 400 page book in 1798 entitled "Initia astronomica" which lists the 
observatory's available technical equipments. Among them were two scientific 
gnomons, one of which is said to have been filar (gnomon filaris, gnomon 
filair, meridienne filaire). Today Martonfi's book is rather difficult to come 
by, there once was a copy in Cluj University library, but that has since 
vanished (perhaps it was stolen and sold off to collectors). So far I have been 
unable to gain access inside the Observatory in Alba Iulia and actually see 
what remains of these gnomons, but I managed to obtain a photo showing what 
appears to be a trap door on the wooden floor of the observing room, presumably 
with a cable running underneath up to the wall in the back, ending with a 
suspended weight (see enclosed). I've done some research and it seems this kind 
of sundial was first described by German physicist Christian Gottlieb 
Kratzenstein in 1782. A detailed description and drawing are also available in 
the work "Beschreibung der meteorologischen Instrumente" by Augustin Stark, a 
copy of which can be read here: 
http://www.e-rara.ch/zut/content/titleinfo/6013342 


Have a look at the drawing on the left of Tab. V on page 100. There light 
enters through a 2 mm hole drilled in a metal plate which is fixed outside the 
southern window, parallel to the equator, and the meridian cable runs across 
the roof of the room and also ends in a weight. From it you had to suspend one 
or more vertical wires, the shadows of which caught on a piece of paper were 
used to time solar transits. But contrary to the filar gnomon presented in this 
book, the meridian cable from the old observatory in Alba Iulia appears to run 
UNDER the floor so I am unsure how it was used. The question also arises 
whether there still are any similar working filar gnomons left in other old 
astronomical observatories.


Dan Uza





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