Note: I have decided to add questions and answers that I get via email to this page:
How can I determine the amount of solar shading for a potential solar site?
There is a simple device, a "Pathfinder".
You place this device at the potential location for the solar panels.
You then trace a line on the paper under the dome. Once done, you will have a good idea of the total solar output year-round. Of course, we can't predict the weather..