This was 'photoshopped' before Photoshop was invented. Old school in-camera double-exposure. You would take one photo, but not advance the film to the next frame. Then take another photo on top of the first exposure. In this case, the bridge was shot with a wide angle lens and the moon was shot with a 1000mm mirror lens. There was a lot of guess work and some rules of thumb for exposure that I've long since forgot. And then you didn't know if anything turned out until days later.
