Now that I've seen the news on the stolen equatorial in Germany, I remember I once made a similar design for Pov-Ray (a 3D renderer). it was an equatorial with a spindle-shaped gnomon so that it showed true (or legal) time, instead of solar time. The gnomon was rendered by brute force, this is, cutting a cylinder with rays from the hour points to the sun, but I wonder how could I derive some implicit or, better, parametric equations for such gnomon in order to introduce them in a CNC machine, for instance.
Hello Anselmo and others sundialists, I'm not sure if this is exactly what you need but you'll find such equations in an old report of mine available in the address http://www.math.tut.fi/~ruohonen/SundialRep.pdf Two gnomons are needed, one for spring and one for autumn. Both gnomons are rotational surfaces, and both contain a sharp point in the middle (spindle). The sharp point can be avoided by using shifted time, as explained in the report, which might come in handy when CNC lathes are used. But there is a problem. As explained in the report, the exact mathematical shapes of the gnomons do not exist, because of singularities near the solstices. Excluding a few weeks around both solstices, or using approximate shapes is a workaround for the problem. Several such constructs are explained in the report. Hope this is of some help, Keijo Ruohonen *************************************************** Keijo Ruohonen Tampere University of Technology (+358) (3) 3115 2420 Institute of Mathematics [EMAIL PROTECTED] 33101 Tampere http://math.tut.fi/~ruohonen/english.html Finland **********************************NULLIUS*IN*VERBA* -
