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Hi Peter,
For a mathematical and practical analysis, see 
Ortwin Feustel, 'Ivory Sundials of Nuremberg Incorporating a Scaphe Sundial' 
BSS Bulletin 24(ii) 36-42.
Regards,
John------------------------
Dr J Davis
Flowton Dials http://www.flowton-dials.co.uk/
BSS Editor http://sundialsoc.org.uk/publications/the-bss-bulletin/
 

    On Tuesday, 7 April 2020, 12:07:28 BST, Peter Mayer 
<[email protected]> wrote:  
 
   
Hi, 
   Dan-George Uza's recent post reminded me of a question I have. I was looking 
at Mark Lennox-Boyd's lovely Sundials the other day, especially photos of some 
of the beautiful Renaissance ivory diptychs, and realised that I didn't 
understand the principles behind the small scaphes on many dials. (Here's a 
Wikicommons photo of a Leonhard Miller dial). 
 The Greek and Roman scaphes, like the one in Dan-George's photo, were hollow 
sections of either spheres or cones, with a gnomon at their centre. Their mode 
of operation seems quite straight-forward.
 But the scaphes in diptyches weren't like that. They appear to be tiny slices 
of much larger spheres. And the gnomons are, of course, far from the centre. 
The 'furniture' on several of them seems similar to stereographic projections. 
But, since instrument-makers then were well able to make astrolabes with 
stereographs, perhaps not.
 So: can someone point me to an article which discusses these small scaphes? 
Or, in the meantime, help me understand how and why they were used? Why don't 
we make them any more? Or: are there any contemporary examples, using, say, 
bowls, or bird-baths or skateboard parks?
 best wishes,
 
 Peter
 
 -----------
Peter Mayer
Department of Politics & International Relations (POLIR)
School of Social Sciences
http://www.arts.adelaide.edu.au/polis/
The University of Adelaide, AUSTRALIA 5005
Ph : +61 8 8313 5609
Fax : +61 8 8313 3443
e-mail: [email protected]
CRICOS Provider Number 00123M
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