I know that's what he meant, Caleb, but I was confused by this part:
The MBED reads voltage from two small photovoltaic cells placed at right angles to each other. It rotates until the voltages on the two panels match. However, Davis found that this did not work in the Arizona sun as well as it did on his Florida workbench. The sun was too bright, and the difference between the panels was too minimal at any angle.
That made me wonder, if the Arizona sun was too bright, then why not make it less bright with a filtering lens? Wouldn't an opaque shade cast a longer and longer shadow as it tilts, thereby throwing off the direction more and more? I'm not getting that part.
The entire point was to make them uneven so that the array would shift to put them back in an even state. Without the shade, both panels reached saturation at all times. The shade gives a mechanical means of increasing the disparity between the two.
I wonder, instead of using the shade, wouldn't it have been better to simple put a light-absorbing filter over the photovoltaic cells? The shade would shift in angle, exposing more of one cell than the other, while a filter would keep them even -- replicating Florida in Arizona.