Hello again: Was just thinking about incorporating a vertical gnomon/nodus into the design of my giant sundial, which we discussed several weeks ago. In addition to the thick cable hour line style, I could place a tall flagpole south of center for the vertical gnomon. The brass ball that is on the top of many common flagpoles could serve as the nodus. But I'd have to be careful that the ball is the right size. The nodus might have to be custom made.
By the way, I did shadow casting experiments to see how well a very pointed 10 " gnomon/nodus cast a shadow. (The 9 degree point is almost exactly the same point made by the average pencil sharpener, so I used a pencil point in my experiment). Mac, I know that you were concerned that this point would cast a poor, indistinct shadow, but I found out that blunting (filing down) the tip of the point to give a 1/16 " circle at the top solved the problem. I'm sure that you are right that taller noduses would work better if they were spheres insted of points. Also, slightly blunting the tip of the pointed nodus makes it a little less dangerous! John Carmichael http//www.azstarnet.com/~pappas
