Before we dive into the moonlit firefall, let me quickly explain how the more popular firefall event works. That is, the one driven by direct sunlight during sunset.
It’s basically a rare event that happens in specific dates when the sun is about to set (so you get the typical “golden hour” colors) and its rays only hit in the thin area on the El Capitan walls right behind Horsetail Fall, reflecting it right against the waterfall, causing the effect that the water is indeed red or golden color, almost lava-like. Several things must come together for a firefall to form, though… More at Deep Sky Colors.
Understanding what is behind a photo is one thing, but it is rare for it to be worth all of the talk. Quite wonderful.