Re: A question abou scaphes
On Tue, Apr 7, 2020 at 12:24 PM Michael Ossipoff wrote: > ...and of course the surrounding flat-dials could, instead, be > Reclining-Declining Dials facing in the cardinal-directions. > > But the sphere-segment indentation surface gives a better continuous > system of dial-lines. > > On Tue, Apr 7, 2020 at 12:18 PM Michael Ossipoff > wrote: > >> If the indentation were a shallow rectangular hollow instead of a segment >> of a sphere, it would of course amount to several adjoined flat dials--a >> horizontal-dial surrounded by vertical-dials. >> >> Michael Ossipoff >> 16 Tu >> Aries 19th >> Aprilis 7th >> >> On Tue, Apr 7, 2020 at 7:07 AM Peter Mayer >> 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 Scienceshttp://www.arts.adelaide.edu.au/polis/ >>> The University of Adelaide, AUSTRALIA 5005 >>> Ph : +61 8 8313 5609 >>> Fax : +61 8 8313 3443 >>> e-mail: peter.ma...@adelaide.edu.au >>> CRICOS Provider Number 00123M >>> --- >>> >>> This email message is intended only for the addressee(s) >>> and contains information that may be confidential >>> and/or copyright. If you are not the intended recipient >>> please notify the sender by reply email >>> and immediately delete this email. >>> Use, disclosure or reproduction of this email by anyone >>> other than the intended recipient(s) is strictly prohibited. >>> No representation is made that this email or any attachment >>> are free of viruses. Virus scanning is recommended and is the >>> responsibility of the recipient. >>> -- >>> >>> --- >>> https://lists.uni-koeln.de/mailman/listinfo/sundial >>> >>> --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: A question abou scaphes
If the indentation were a shallow rectangular hollow instead of a segment of a sphere, it would of course amount to several adjoined flat dials--a horizontal-dial surrounded by vertical-dials. Michael Ossipoff 16 Tu Aries 19th Aprilis 7th On Tue, Apr 7, 2020 at 7:07 AM Peter Mayer 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 Scienceshttp://www.arts.adelaide.edu.au/polis/ > The University of Adelaide, AUSTRALIA 5005 > Ph : +61 8 8313 5609 > Fax : +61 8 8313 3443 > e-mail: peter.ma...@adelaide.edu.au > CRICOS Provider Number 00123M > --- > > This email message is intended only for the addressee(s) > and contains information that may be confidential > and/or copyright. If you are not the intended recipient > please notify the sender by reply email > and immediately delete this email. > Use, disclosure or reproduction of this email by anyone > other than the intended recipient(s) is strictly prohibited. > No representation is made that this email or any attachment > are free of viruses. Virus scanning is recommended and is the > responsibility of the recipient. > -- > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
Re: A question abou scaphes
It seems to me that the indented dial-surface could serve a useful purpose, by ensuring that the nodus's shadow falls on that dial-surface whenever the Dyptich's flat horizontal surface has sunlight. . Maybe it's desired to make the indented dial-surface much larger than the hemispherical indentation that could be accomodated by the thickness of the horizontal plate of the Dyptich. . Of course not having the nodus at the center of the sphere would complicate the marking of the lines on the indented spherical surface, explaining why that isn't encountered more often. . It's related to stereographic lines, by having a projection-point not at the center of the sphere. It sounds like a great idea for a birdbath or bowl, but it might be too distracting for a skateboard-park. . Michael Ossipoff Aprilis 7th, 2020 16 Tu Aries 19th On Tue, Apr 7, 2020 at 7:07 AM Peter Mayer 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 Scienceshttp://www.arts.adelaide.edu.au/polis/ > The University of Adelaide, AUSTRALIA 5005 > Ph : +61 8 8313 5609 > Fax : +61 8 8313 3443 > e-mail: peter.ma...@adelaide.edu.au > CRICOS Provider Number 00123M > --- > > This email message is intended only for the addressee(s) > and contains information that may be confidential > and/or copyright. If you are not the intended recipient > please notify the sender by reply email > and immediately delete this email. > Use, disclosure or reproduction of this email by anyone > other than the intended recipient(s) is strictly prohibited. > No representation is made that this email or any attachment > are free of viruses. Virus scanning is recommended and is the > responsibility of the recipient. > -- > > --- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --- https://lists.uni-koeln.de/mailman/listinfo/sundial
