Solar PathFinder is a tool which allows you to record the sun's path at your location.
All you need to do this buy this expensive product, place it outside and it shows you a trace of sun's trajectory throughout the day.
Obviously this is very interesting but unfortunately not worth the money for most of us.
NASA has been studying the sun, our planet and their relationship for decades. Thanks to this we can tap into their deep knowledge to extrapolate the same information which will then be used to install the solar panels.
Remember: knowing the sun's path is useful only to "tweak" your panel's inclination during installation, therefore a one-time thing.
The price tag on this is $299 and you can check it out here.
A much more affordable solution is implementing a modern smartphone and tablet application like PV Master.
PV Master is very easy to use but will grant you access to a priceless dataset that you will make your jaw drop, not kidding.
Based on your current GPS location, you will be able to access all the historical data, gathered directly by NASA, in order to best install your beloved solar and photovoltaic panels.
In addition, you will also have all the tools, guides, calculators and glossary essential to properly make the best of your renewable energy system.
Check out PV Master.