Comment "bright as a full moon" (Score 3, Insightful) 80
You can stare at the full moon all night if you like, because the albedo of the moon has filtered most of the light including the UV band that naturally passes through our own atmosphere. The three mile circle illuminated by a mirror would bounce a significantly higher amount of UV than the moon's albedo. If you treat the 60ft reflector as an analog to a pinhole in a pinhole camera, the circular area on the Earth surface would be a rough projection of the image of the sun.
(1) I wonder how they calculate the UV exposure for the observer on the surface within the illumination area.
(2) I wonder if you'd be able to detect places in a coherent projection where sunspots or coronal ejections are reflected through the "pinhole" effect of this arrangement.