Effects like that are one of those things I have to give a pass to sci fi shows. Sure Gravity and Interstellar did a great job showing spaceflight, velocity differences, etc, but audiences used to Star Wars and Star Trek are still not ready of it, visually. Photon torpedos must casually loaf along slower than a golf cart, X-wings must battle Tie fighters like World War I biplanes at similar velocities.
There is no way of knowing where that window was located on the ship, so it appears like it broadsided them, which means they should have seen it for a very long time as it was on a similar velocity and trajectory to hit like that. If it hit their bow, someone was asleep at the wheel and apparently asleep and their radar didn't work. If it hit them astern.. ok I got nothing.