the skywalkers

following a link in the ep2/3 forum, how and when did Vader learn that Luke was his son, i find it hard to believe that it was at the end of anh and i can't find a point in esb where vader suddenly thinks, oh that was him. Is there not some text at the start of esb that says that vader is lookinf for luke?

Indeed. Clearly it was some point between ANH and ESB, and I would guess it was the hailing of the new Rebel hero 'Commander SKYWALKER' that gave him the clue.

Then he probably traced back the events- Obi-Wans' appearance, the Princesses ship fleeing to Tatooine- and put two and two together.

I remember the very EU comic book story where Vader finds out the name of the one who destroyed the Death Star I. Now, this is not canon of course, but we can safely assume that he found out somehow through his spies. He also felt that the force was strong with the one who destroyed the DSI, add that up with OB1 and there you go. It doesn't really matter though how exactly.

But we know he has found out before ESB starts by this very line: "That is the system and I'm sure Skywalker is with them." Can't be anyone else but his son.

I think that he knew all along, remember that Vader didn't saw Luke untill the battle at Cloud City, in ANH he only got close to Luke when he was in a TIE and Luke in an X-wing, he said: "The Force is strong in thisone" But he didn't know it was Luke, his son

And I still think that 'The Force is Strong with this one' line just meant he thought the pilot was lucky/skilled! He had no idea that he was actually firing upon a potential Jedi (let alone his son). It's not as if Luke was doing anything that would give away Force power.

The Force is often equated with luck in the Star Wars Universe. If you say the Force is 'with' someone, you don't necessarily mean he is a Jedi, you just mean things are going his way (though you would say that about someone who was a Jedi as well; you'd mean it literally in that case).

'May the Force be with you' says Dodonna, before they go on the mission. He means 'Good luck!', not 'please all develop Jedi powers'!

Likewise this line of Vader's is the equivalent of saying 'this one is a lucky bastard...' as he is trying to shoot him down.

Didn't I say that? Otherwhise sorry, I meant that in anycase

You agree with me, Yerssot? WOO-HOO! You know virtually no-one else here does!

We argued this one out ages ago. Everyone else thinks that Vader was commenting that he had discovered a Force adept.

Well yeah; Vader is using everything he got to shoot him down and he is one of the best pilots of the universe, so he is thinking that Luke doesn't play it 'fair'
meaning that Luke, who is untrained so can't use the Force, can stay out of the blasters, that doesn't mean that Vader sensed him as a potentional Jedi, because than they had to kill nearly everybody in the galaxy

And my allies do grow...

Great kid, don't get cocky!

Well, if you have an opinion, you have to say it. And this is my opinion