This article by Clint Turner (KA7OEI) does a nice job of summarizing the challenges and some solutions :-)
Note that the background for his light source is foliage and a mountain ---- not the sky.
He pretty much confirms much of what we talked about at breakfast today.
Rob - K0XL

https://www.modulatedlight.org/optical_comms/Daylight_Optical_testing1.html