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Hi Sara and all the members of the list,
The ring dial, indeed a good exemple of altitude sundial and elementary
principles of gnomonics applied for a given latitude.
But for a device intended for different latitudes I suppose that it must be
constituted by several (2, 3 or 4?) imbricated rotating parts, how are they
combined to get some thing working without dislocating?
Ali Guerbabi
35.546 N 6.16 E
Le dimanche 29 septembre 2024 à 15:57:20 UTC+1, Schechner, Sara
<[email protected]> a écrit :
Dear Donald,
The proper name for this type of altitude sundial is “ring dial.” Please do
not refer to it as an Aquitaine ring or farmer’s ring. Those were marketing
names used by a modern jeweler.
Many museum collections have ring dials, including those at the Adler
Planetarium in Chicago, the National Maritime Museum of Greenwich, the Science
History Museum in Oxford, and others. Most are very simple but others can be
mathematically complex and be adjustable for latitude and season.
I believe R. Newton Mayall and Margaret Mayall give instructions on the
arrangement of hour lines in their book,Sundials.
Good luck with your project.
Sara
Sara J. Schechner, PhD, FAAS
Curator Emerita, Collection of Historical Scientific Instruments, Harvard
University
President, IAU Commission C3 (History of Astronomy)
President, IAU-IUHPST Inter-Union Commission for History of Astronomy (ICHA)
[email protected]
[email protected]
From: sundial <[email protected]>On Behalf Of Donald Christensen
Sent: Sunday, September 29, 2024 2:10 AM
To: Steve Lelievre <[email protected]>
Cc: Sundial mailing list <[email protected]>
Subject: Re: portable sundial
Thanks for the info. Do you know where I can find the mathematical
calculations? I'd like to make one
Cheers
Donald Christensen
0467 332 227
If you focus on what you lack, you'll lose what you have. If you focus on what
you have, you gain what you lack.
On Sun, Sep 29, 2024 at 3:29 PM Steve Lelievre
<[email protected]> wrote:
Hi,
It sounds to me like a reference to what is sometimes called an Aquitaine Ring
(because of a story that Elenor of Aquitaine gave one to her husband to be).
Also known as a Farmer’s Ring.
Modern ones are readily available. Just search the internet for “Aquitaine Ring”
Steve
On Sat, 28 Sep 2024 at 20:53, Donald Christensen <[email protected]>
wrote:
In the book,
Sundials: Their Theory and Construction Paperback – 1 June 1973
by ALBERT WAUGH (Author)
He explained a portable sundial that worked similar to a shepard’s dial.
Instead of a gnomon that cast a shadow on the pillar, this looked more like a
ring. Instead of a shadow that told the time, a beam of light showed through a
hole in the ring. There were groves on the inside of the ring. Time was read by
inspecting wherever the beam of light touched one of these grooves. The ring
would hang from a string.
Does anyone have any information about this sundial?
Cheers
Donald Christensen
0467 332 227
If you focus on what you lack, you'll lose what you have. If you focus on what
you have, you gain what you lack.
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