It sounds reasonable, Fer.
But your explanation belongs to the history of time keeping and is
not common knowledge of an ordinary citizen walking in an Italian city.
Therfore I aggree with your suggestion; "a build in correction would
have been easier in use".
And that has'nt to cost 275,000 dollar! To become a not accurate
mechincal system!
Let's do it with electronics (eventual in combination with GPS). It
will be cheap and accurate.
I did it in a simple Excel worksheet on my computer. One can see a
picture at the website of Frans Maes http://www.fransmaes.nl/
zonnewijzers/welcome-e.htm
in the category 'Miscellaneous types' - click on the picture above
'Virtual sundial Hasselt'
Best regards.
Willy LEENDERS
Hasselt in Flanders (Belgium, for the time being)
www.wijzerweb.be
Op 5-aug-08, om 10:20 heeft fer de vries het volgende geschreven:
Willy,
In the past local suntime was used for civil time.
A sundial was the leading instrument.
When a clock was placed on the church the clock was regulated by
the parish clerk to local suntime with the help of a sundial.
This is why we often see a clock and a sundial on one building.
As people got their clock at home a table for the EoT was delivered
with it so they could regulate the clock at home for local suntime.
Some clocks had the EoT correction build in to keep it running
local suntime.
If I follow this story it isn't strange to me to see the
combination of a clock with a second mechanical dial for the EoT,
however, a build in correction would have been easier in use.
Sounds this reasonable?
Best wishes, Fer.
Fer J. de Vries
De Zonnewijzerkring
http://www.de-zonnewijzerkring.nl
Molens
http://www.collsemolen.dse.nl
Eindhoven, Netherlands
lat. 51:30 N long. 5:30 E
----- Original Message -----
From: Willy Leenders
To: Frank King
Cc: sundial
Sent: Monday, August 04, 2008 6:37 PM
Subject: Re: Equazione del Tempo
What is the importance for an ordinary citizen to have an
indication of EOT nearby a clock that indicates civil time? He
does not know what this is and if he wants to know the time as a
sundial indicates, he has to calculate and he should also bring in
account the time difference by the difference in longitude and the
summertime.
Would it not be better to design a clock that indicates immediately
the 'sundial time'?
Willy LEENDERS
Hasselt in Flanders (Belgium)
www.wijzerweb.be
Op 4-aug-08, om 11:06 heeft Frank King het volgende geschreven:
Dear All,
Next to a sundial it is quite common to see
a representation of the Equation of Time.
One reason for this is so that people can
note the time shown on the dial and then
calculate the time that should be shown on
a clock.
There is an implicit assumption that clock
time is what the user really wants to know
and that sundial time is somehow inferior.
In Italy they think the other way round...
Take a look at:
http://www.cl.cam.ac.uk/users/fhk1/EofT.jpg
Here you will see an ordinary public clock
showing 12:51 and immediately below the
clock is a second clock with a single hand
that indicates the EQUAZIONE DEL TEMPO. In
the photograph it shows -6 minutes.
Here people can note the time on the clock and
calculate the time that should be shown on a
sundial!
The implicit assumption is that sundial time
is what the user really wants to know and that
clock time is somehow inferior.
Bravo to the Italians!
The photograph was taken on 1 August when the
Equation of Time was indeed about -6 minutes.
The main clock was showing Central European
Summer Time.
I do not know of a public (outdoor) clock in
the U.K. that shows the Equation of Time and
wonder how much demand there would be for
such a facililty?
For completeness: the photograph was taken
in Piazza Dante in Naples.
Frank King
Cambridge, U.K.
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