Here’s a Solar Pathfinder in action on my roof. But what does it do? Glad you asked. From the solarpathfinder web site:
The Solar Pathfinder determines and records year-round, site-specific solar data. More specifically, the monthly sun path diagrams contain 12 horizontal arcs, one for each month; as well as vertical lines for solar time. Each arc shows the mean sun’s path across the sky for that month. The sun path arc for December is the farthest from the center of the Pathfinder, showing the lowest winter sun path through the sky. The arc for June is closest to the center, showing the highest summer sun path
Bottom line — the Pathfinder will show exactly what times of day and months of the year shade and fall will fall on any given site. Essential information for any solar installation!