THE PATENTS
1867 US Patent by L.Miflin for Shaped Style Dial
1892 UK Patent by Major John Ryder Oliver for Shaped Style Dial
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PIERCED STYLE DIALS
In this class, the each half of the analemma is encoded in either side of the style.
Ken Clark - Schmoyer Dial 2018
3-D printed Schmoyer dial by Bill Gottesman, www.precisionsundials.com (
Tony Moss 'Henry Moore' dial - ca 2010 - note the clever arrangement to ensure that the plane of the analemma is perpendicular to the sun's rays
Pete Swanstrom - www.swanstrom.net/sundial/ - Ann Morrison Park, Boise, Idaho - 1998
Pete Swanstrom - www.swanstrom.net/sundial/ - New Millennium Dial - 2018
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SHAPED STYLE DIALS
In all cases, in this class, the shape of the analemma (or half of it) is encoded in the style. If the style is symmetrical, it must encode half the analemma. In which case, two interchangeable styles must be provided) - with exceptions (see below)
Mean Time Sundials with polar cone and vertical cone gnomons - Hendrix Hollander - www.analemma.nl - ref NASS Compendium v13(3) Sept 2006 - 2 articles : Mean Time Sundial With A Cone Gnomon & Bi-Gnomon Sundials
Mean Time Sundials with polar cone and vertical cone gnomons - Hendrix Hollander - www.analemma.nl - ref NASS Compendium v13(3) Sept 2006 - 2 articles : Mean Time Sundial With A Cone Gnomon & Bi-Gnomon Sundials
Rolf Wieland : There are two shaped styles : each representing half the analemma : Ref NASS Compendium v18(2) June 2011
Martin Bernhard' s dial at the Stuttgart Planetarium
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THE INTEGRATED DOUBLE GNOMON SUNDIAL OF WERNER RIEGLER
This unique idea has been realised in 2003 by Werner Riegler in Joannes Kepler's city of Linz. 
The solid inner and transparent outer parts of the Style
the Dial in section
Detail of the lower half of the dial
How the dial is read in the sun-ascending & sun-descending halves of the year
Werner Riegler at the installation
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As modelled
In reality
The dial also contains a calendar. When the time is being read on one side of the dial, one of the two possible dates can be read from the shadow of the dial rim on the other side of the dial.​​​​​​​. Click on images to enlarge & view captions
the top half of the style
the bottom half
the two previous images merged to show the analemma
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For more detail, read below
ERRORS USING A SINGLE SYMMETRICAL GNOMON THROUGHOUT THE YEAR
Werner Riegler has analysed this situation in the following paper. In summary, a symmetrical gnomon can be made that will work with errors not exceeding 1.7 minutes of time. However such a gnomon will not work for some 10 days around the winter solstice and for some 2 days around the summer solstice. During these periods, the correction for one day shadows the correction of the next day. Thus, such a gnomon can only exist in the declination range -23.30° to 23.42°
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