Hi John,
> The gnomon would be on the outside of the window and the plastic film on the > inside, so drilling a hole is unnecessary if you use adhesive for the > gnomon. This arrangement is more complex than it might appear at first thought. Mike Shaw has been down this road and that is what his double pane dial prototype demonstrates...the nodus is on the outer pane and the shadowfield is on the inner pane. Go to his sundial page (referenced on the SGS page) and have a read...I am sure that he would be happy to help you understand some of the difficulties he encountered. One other thing bears mentioning. Every time a ray of light passes through a pane of glass a certain amount is lost due to incidence reflection at the surface, especially at low angles. That is how you can see yourself in a storefront window. The more panes the shadow has to pass through, the dimmer it will be by the time it gets to the surface of the shadowfield. This includes any protective coverings as well... Jim -
