Instead of having a machine that moves through spacetime, you could have one that pushes its contents through spacetime. The machine acts as a tether through space. Of course this would limit time travel to the initial existence of said machine and when it still exists in the future.

You could also just make a spaceship that travels through time. You still have to calculate positions of objects flying around the universe but at least you don't have to figure out how to appear precisely wherever Hitler was in Germany in 1933. (In this scenario we are stopping Hitler before he becomes chancellor, not trying to kill him as a baby. We are not time-travelling monsters.)