Ron Anthony has kindly given me a brief explanation (see below) of the movable style mean time dial to which he referred and pointed me to Yvon Masse's web site where there is a full description of this interesting and ingenious dial.
The English version of a relevant page is at http://www.apro.fr/usr/ymasse/anmn2.htm Andrew James Ron Anthony [EMAIL PROTECTED] wrote: <snip> Here is my explanation of what he was saying. 1. Set up an armillary dial with a horizontal surface under it. 2. Pick a point (O) on the equatorial ring, say OPPOSITE from the 10 am hour mark. This point is the fixed point O in the diagram. 3. Project from that point through each of the hour lines onto the horizontal surface. This will result in a set of hour lines that are on a straight line. 4. By some math/graphical magic, he shrinks the size of the equatorial ring BUT keeps point O and one of the hour points. A projection of this new ring gives the same hour points on the horizontal surface. 5. By having the string always starting at point O and passing through the correct spot on the new pole style for each date he is able to shift the EoT. The other end of the string is determined by point O and the correct spot on the style. In practice the dial could be a post where the top is O, and the hour lines and analemma are painted on the ground. Simple dial, No? Compendium 5-1 contained a BASIC program to draw it. ++ron
