Dear Rolf, Many thanks for that diagram. It makes everything very clear.
Where I live, at 52N, there is very little change in the width of the shadow of a rod gnomon over the course of the day. Almost no one notices it. In the tropics, the change is much more obvious. You can see why I chose 30N for my example! Very best wishes Frank --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
