Hello All,
I am a little confused: Who made this dial?
I think it is magnificent. The setting is stunning, the rock
mounting is dramatic. This is a first-class project.
I would be interested in reading (in English) how it was mounted,
how it was aligned, how it was engraved, how the discs are
mechanically assembled and what kind of bearings are used to
minimize play. I hope an article in the NASS Compendium, or the BSS
Journal is forthcoming.
Although the Renaissance double focusing dial can be read to
within 10 seconds, in practice it has mostly only been accurate
to within 1 minute, and sometimes worse. This is because the
Equation-of time is an average over the current 4 year cycle, and is
further due to imperfections in the roundness and concentricity of
the helix and imperfections in polar alignment.
-Bill Gottesman
On 6/25/2012 3:55 PM, Frans W. Maes
wrote:
Dear
Fabio, Roger & all,
It is always interesting and instructive to consider claims of
extraordinary properties; in this case, a temporal accuracy of 10
seconds. The final accuracy of a sundial is the result of several
factors, among which the accuracy of orientation and mounting.
However, the basic factor here is the accuracy with which a hair
line can be placed in the exact center of a strip of light by
rotating a disk. The attached photo nr. 7 from the following pdf,
taken from Fabio's site:
http://www.sundialatlas.eu/photo/CH/156/CH000220_2_A.pdf
sets the stage. The slit (the gnomon) is placed at the center of
rotation of the disk that carries the hair line.
Ten seconds of time corresponds to a rotation of 2.5 minutes of
arc around the polar axis. So the question is: can the hair line
be placed on the theoretical center line of the light strip with
an accuracy of 2.5 arcminutes? I think that only actual
experiments can answer this question, but I am doubtful.
The edges of the light strip are sharpest close to the gnomon, but
the lateral displacement of the hair line due to rotation is small
there. Further out (to the right in Fig. 7) the light strip gets
wider, with fuzzier edges. What would be the best distance from
the gnomon to look for estimating the center? And what accuracy
would be feasible? Does anyone know about experimental data on
such a task?
As far as I know, the only case where a reading accuracy of 10
seconds of time is achieved, is in the double focusing sundial of
Bill Gottesman; see:
http://www.precisionsundials.com/sundial_list.htm (scroll all the
way down).
Best regards,
Frans Maes
On 24-6-2012 20:09, Fabio nonvedolora wrote:
On Sundial Atlas there is the card of this
sundial with 4 pdf files
attached, one of them with technical info. All of them are in
german.
www.sundialatlas.eu/atlas.php?so=CH220
ciao Fabio
Fabio Savian
fabio.sav...@nonvedolora.it
Paderno Dugnano, Milano, Italy
45° 34' 10'' N, 9° 10' 9'' E, GMT+1 (DST +2)
From: Reinhold Kriegler
Sent: Sunday, June 24, 2012 4:39 PM
To: Sundial Mailingliste
Subject: The most exact sundial of the world> In Samedan!
Dear friends! Have a look to Switzerland!
Genaueste Sonnenuhr der Welt steht im Engadin
Auf Muottas Muragl auf 2456 Meter über Meer ist am Donnerstag
die genaueste Sonnenuhr der Welt eingeweiht worden.
a..
http://www.bote.ch/vermischtes/genaueste-sonnenuhr-der-welt-steht-im-engadin
Quelle: suedostschweiz.ch
b.. Datum: 22.06.2012, 17:00 Uhr
c.. Webcode: 39872
O I “love” the superlatives in connection with sundials!! :-)
So far this one I did not know: “The most exact sundial of the
world!”
Best regards
Reinhold Kriegler
* ** *** **** ***** ****** *******
Reinhold R. Kriegler
Lat. 53° 6' 52,6" Nord; Long. 8° 53' 52,3 Ost; 48 m ü. N.N.
GMT +1 (DST +2) www.ta-dip.de
http://www.ta-dip.de/dies-und-das/r-e-i-n-h-o-l-d.html
http://www.ta-dip.de/salon-der-astronomen/bewohner-des-salons-der-astronomen.html
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