Whenever a ship jumps to hyperspace in Star Wars, a lot of times you’ll hear the pursuers say something along the lines of “plot every course from their last known trajectory.” Since pretty much all hyperspace lanes are widely known, a ship can be somewhat tracked even after jumping into hyperspace. I’m guessing this is at least somewhat useful since Vader himself tells them to use this tactic at times in the OT. I guess this is one of the times that it worked, which is why he would tell his officers to use that same tactic later on.
This requires EU logic but the best i can do (as a Game master for alot of starwars Rps)
Hyperspace pathways are logged. When you use a pathway you are following coordinates from probes in space. that are constantly updated and are tracked. No one just hops around in hyperspace other wise you will end up jumping into a black hole or an asteroid field, or worst, another ship. This data is accessible by the local governments that maintain them, and even charge a fee for usages. Its why the Local Governments can set up Grav-Wells to pull ships out of hyperspace at safe points for inspection. Think of this as GPS data. but every car has one. and the local police can pull logs of who has been going through the lanes. So in theory The Imperial Fleet would be able to pull the log from the hyperspace lanes and follow along. A diplomatic vessel on a diplomatic mission, (which is what Leia stated in New hope she was doing) Would have to log their course with the Senate to make sure the lanes are clear, and there hasnt been any reported pirates in the area. Think when government officials visit states. They have to let the local police know so they can clear streets, and provide security. When a diplomat would be going on a mission they would be using official lanes and jump data other wise they would look very suspicious and would give Imperial Fleet a reason to pull them out of hyperspace.
Of course none of this matters when you park above a planet thats marked off limits, in the middle of a rebellion space fight. Have people Manually board your ship to hand over codes then attempt to fly away.
However this is Disney Star wars so they didnt think about any of this and just said. Cause we said so and they wanted a cool vader scene and logic be dammed.