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) sara_schech...@comcast.net<mailto:sara_schech...@comcast.net> sche...@fas.harvard.edu<mailto:sche...@fas.harvard.edu> From: sundial <sundial-boun...@uni-koeln.de> On Behalf Of Donald Christensen Sent: Sunday, September 29, 2024 2:10 AM To: Steve Lelievre <steve.lelievre.can...@gmail.com> Cc: Sundial mailing list <sundial@uni-koeln.de> 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 <steve.lelievre.can...@gmail.com<mailto:steve.lelievre.can...@gmail.com>> 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 <dchristensen...@gmail.com<mailto:dchristensen...@gmail.com>> 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. --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial<https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.uni-2Dkoeln.de_mailman_listinfo_sundial&d=DwMFaQ&c=WO-RGvefibhHBZq3fL85hQ&r=7ZsgDX5inZSMERqhZEQacOtdADP0iy6-YB7dx6Z_mVo&m=-SrZOYJ-paV1yxzcIhs8m-_Dma17c80GrTmCC9S0oSfYMgF0wYsciPcALYg3pDSS&s=QJYZ6mQiZlB_t7621yVCIb3zcYIJfssk3k9lb6aMIlA&e=>
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