Similar high-speed rotating mirrored cameras were used to record US atomic and hydrogen bomb tests, especially in the first very tiny fractions (micro?/nano?/pico)? of a second after the birth of the fireball. I remember seeing photos shot through the window of the enclosed structure at the top of the tower, of an A-bom fireball, only a few feet across, and not yet even large enough to envelope and destroy the structure. The fireball at that age looks very much like a grain of spikey pollen.