Hi John, Perhaps I was a bit too general in my last posting, because I can see problems if the protective acrylic window was bowed and not perfectly flat. Looking at some of the replacement windows in my garage door, the acrylic ones are not as flat as the glass ones, and I would assume that the rays are shifted as a result. Actually there are optical imperfections in automotive glass too, if you really think about it.
I would say that if the outer protective window was of good quality and flat, it probably would not pose a problem...but I don't know about putting the gnomon on the outside of it. That is probably best discouraged as far as the "glassers" go. Jim -
