On Tue, 22 Oct 2002, Frans W. Maes wrote: > In my view, however, the most promising development has not yet been > mentioned, neither in the BBS article nor on this list: the shadow plane or > hour plane sundial. > 2). Wider dissemination was given, among > others, by the articles of Maddux, Oglesby & De Vries (see > http://home.iae.nl/users/ferdv/shadow.htm).
Since this concept was raised on the maillist and inthe Compendium, I have also been intrigued by the freedoms it can offer to a designer. Since Frans' posting, I re-visited Fer's site, and looked once again at the diverse implementations there. I was struck by the way Mac Oglesby's string-and-diptych dial illustrated the very simple idea of the shadow plane, and relates it to one of the best geometric dials, the armilary sphere! Look at Mac's dial picture, http://home.iae.nl/users/ferdv/shad3-2.htm and visualize the missing central shaft of the armillary, running in this case, from the vertical dial center to the horizontal dial center. There, perfectly set for 11:00 AM, is the string shadow, the extension of a shadow from the equatorial ring, onto the axis... Once we see how this works in an armillary, it's a short step to separating the planes by translating them, parallel to the polar axis, to wherever we want them. Dave 37.28N 121.97W -
