Dear Fred and all, I'm sorry about my previous email regarding this subject, I hadn't read the articles in the repository regarding the use of Maple/Matlab in the design of sundials in the NASS Repository. Now that I have, I see there is still work going on in this area. One small change I'd make to these two articles is in the regard to the curves being called Astroid curves. An Astroid curve being a Hypocycloid of 4 cusps with a formula of x=A*cos^3(Theta), y=A*sin^3(Theta). Rather it is probably the Evolute of an Ellipse with the formula x=A*cos^3(Theta), y=B*sin^3(Theta) where A=(a^2-b^2)/a, B=(a^2- b^2)/b where a and b are the semiaxes of the ellipse. This would account for the change in shape viewed from inclined planes. But, then, I'm not a mathematician, nor expert on these programs, so I would be very glad to hear from others on this.
Thanks for the patience, Edley McKnight [43.126N 123.526W]
