Why doesn't Vader's shot hit Luke's x-wing?

This apparently needs it's own thread.

Episode 4, on the trench run. Vader lines up his shot, says 'i have you now', and fires.

THEN Han shoots Vader's wing man and careens off into space.

That's always bothered me. What am I missing? I could see if Han's shot hit the wing man who then bumps Vader's Tie Fighter causing him to miss the shot, but that's clearly not what happens. Is that they way that scene is supposed to be interpreted?


Why doesn't Vader's shot hit Luke's x-wing?