Hi all, a few weeks ago Mr. Siegfried Netzband has requested some explanations about the Trifilar Sundial invented by prof. Bernard Rouxel and Fabio Savian has sent to the Sundial list a copy of the original paper translated in Italian and published on the "XV Seminario di Gnomonica". So I am pleased to post to this list a link where you can find an animation used during the presentation of the paper in order to show this Rouxel's masterpiece at work
https://youtu.be/5psGMuzcTyM The animation has be made by me with the help of Tonino Tasselli and has been computed for the summer solstice day. On the sundial plane the tree wires shadows, crossing each other, form a moving triangle. The triangle becoming smaller and smaller collapses into a point exactly at noon. The point where the triangles collapse during the year migrates up and down along the green lines so this line is the meridian line and may be quoted with dates or zodiac symbols. Anyway with a different arrangement of the tree wires (for example with a rotation of the whole wire system about the polar axis) you can obtain the triple crossing in a point moving along hour lines other than noon. Best salutations Luigi Ghia
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