If I may, I'd like to offer an opinion\possible explanation for the concerns from the few posts above.
We're discussing a movie from the 1970s. That was a different time - a more innocent time. Uber-realism - whether it was story, graphic violence, hate, fear, blood, etc - was not the style of the time, nor the expectation. At least not where an outer space adventure was concerned.
We were concerned with hoping Luke, the Princess, and the others got away from the Death Star - not the minutia of exactly how the device was placed, when, by whom, or how it worked within the framework of the Empire's plans.
Star Wars captured the world in 1977 because it was - as it is often referred to - a fairy tale. It wasn't a shaky-cam, F-bomb laden, close-up-of-the-exit-wound affair.
Different decade - different film experience.