star wars - Why does Darth Vader need to use a targeting grid on his Tie Advanced in ANH?

When Darth Vader - one of the best pilots and shooters in the Galaxy thanks to being a powerful Force user and Sith Lord - is hunting for rebel starfighters above Death Star in his Tie Advanced x1 fighter, why does he rely on his fighter's targeting system instead of The Force?

Obviously, out of universe, showing the process of locking onto a target is good action movie visual. But was that retconned in-Universe?

Answer

If he had been the younger version of himself with his limbs intact, he would not have needed a targeting computer. Not even against Luke. He did pod racing and flew a fighter straight into a Trade Federation ship while dodging a lot of enemy fire. He did all that while he was a kid with no Jedi training.

But when he is controlling his prosthetic limbs, no midichlorians are involved. As with any prosthetic, his motor nerve signals will be picked up by sensors in his stumps. Then they'll be converted to electrical impulses that drive the servos of his arms and hands. The same probably applies to his eye instruments, in reverse. They may not have the same acuity as his real eyes.

So he may have the reflexes of a Jedi/Sith, but his body is the bottleneck. He cannot use the Force to directly guide his eyes and hands. This is probably the same reason why both Obi-Wan and Luke lasted as long as they did against Vader during lightsaber duels (in ANH and ESB respectively).