So, they have the Starkiller. Big bang, faster than lightspeed superweapon that blows up planets. Ok. Fine.
But how do they see it?
The good guys are standing on the surface of a planet and look up and see the big red glow and boom.
So were they in the same solar as the target? Was there some other effect letting them see it at FTL speeds? Has no-one making the film heard of the speed of light?