Ken Clark and All,
The large amount of interest in this topic has stimulated me to add one
more contribution.
On page 30 of the NASS Compendium for September 2000 there is a diagram
of a self similar rosette pattern. If this pattern is reduced to an
appropriate size (say 1 inch diameter) onto transparent plastic and mounted,
with its plane parallel to the sundial surface, at the point where the nodus
would ordinarily be, it will serve the purpose of a nodus. Surprisingly, the
shadow it makes will be equally sharp and well defined regardless of the
distance to the dial plate.
As far as I know this is a new type of nodus (invented by Dale Walton)
and a new use for a self similar, or fractal, pattern. It may present a
clumsy appearance at first, but the shadow it produces is beautiful and might
be worth incorporating into an artistic dial.
May your shadows always be sharp.
Bill Walton
41d 58m N,
70d 41m W
