Hello all: I was just thinking that on a horizontal sundial that the true shadow point would ONLY be at the center of the penumbra at high (apparent) noon. In the late afternoon or early morning, the sun would be to the side of the style, causing the shadow to strike the dial face at an angle. Wouldn't this shift the true shadow point towards the center of the sundial, away from the center of the penumbra? (wish I could make you a little drawing of this as a picture is worth a thousand words).
John Carmichael >
