Thibaud Taudin-Chabot wrote: > That sundial is not 1 spot projected on the floor, but the whole > sundial pattern projected on the floor. On the floor you only need 1 > readingmark, nothing more.
I understand; I mentioned it as an example of dark spots being projected on the receiving surface, only... > But the shadow of a spot on a window will be very difficult to find on > a sunlit floor because the light of the sunlit floor is reflecting in > every direction and also over the shadow spot so that shadow spot will be > less clear. > The bright spot of sunlight from a hole in a closed wall/ceiling will > therefore much easier to find in a relative dark area. True! This will impact the choice of surface material, I'm sure. Dave -