I was showing my son some footage of a Saturn V (I don't recall which one) about a minute and a half after launch, and he asked me how they got the footage. All I could tell him was "Chase planes".
Then the other week I found this picture in a book about Apollo 8, in which it says "[...] taken at 35,000 feet by a telescopic camera mounted on the cargo door of a C-135 aircraft."
I've looked high and low for more info and pictures of this set-up, but have managed to find very little beyond what's in the caption of this (awesome) picture.
Does anyone know where on the net or in a book such info might be found? I'd love to give him a proper answer to his question.