Using the tools on SunEarthTools.com I have made a 3D model of the solar ray-cones for our House. We consider buying extra solar panels and I have always wanted to know exaclty what the relative position of the panels to the solar rays is.
The Red cone is june 21st
The Magenta disk is march/sept 21st
The Blue cone is dec 21st
It is clear that the orientation of the house (SW) and the trees, limit the efficiency. A Southern orientation is next to impossible on a steeply sloped roof, so we will have to live with it.
I have prepared a little movie of the 3D model it's on youtube