Here is a video of the shot. It was the fifth largest nuclear shot by the US ever, at 9.3 megatons. It really does look like a sunrise/set (only at 1000x speed).
(I recently read Command and Control, would recommend it, covers a lot of the insanity regarding nuclear weapons. Apparently, up until the 80’s they were surprisingly easy to to set off, none of the PAL stuff you see in movies these days. Right after World War Twi they were still trying to figure out how to work nuclear war into scenario planning, it leads to a lot of crazy phrases like “limited nuclear war” or “progressive escalation” in terms of how to use the weapons not just against the soviets but also against weaker world powers. I think the USA did get a bit of a God complex for a bit, but once the cold war started it balanced it out to a more muted insanity and paranoia as they realized that just about any major power could drop a nuke and it might just set off the rest of the world, intentional or not…)