while we are topic. The Ion Cannon blasts from the planets view, (shot seeing the rebel ships leaving the planet) come from two different origins. We see one set of blasts, then a second. The second batch shifted over to the right a bit from where the first batch came from.
Also, in the shot of the Ion Blast headed towards the Star Destroyer (seen bellow), the laser doesn't appear to be angled correctly. Currently its trajectory looks like its going to miss the Star Destroyer.