Fer, > I have a book by Rafael Solaer, printed in 1989 but I can't find anything > about the Lambert's Circles. > So I can't answer your question because I don't know what was meant.
Oh, it's in the second edition (1996), page 401 but, never mind what he says there, because the problem still stands: is it possible to modify your construction (or maybe the approximate one) so that it shows the insolation hours for *any* vertical flat dial ? And if not, is there any other way to show that? I guess there must be, but I can't see the way. Anselmo
