Forum:KB:What was public knowledge?

When something shocking is revealed in the Star Wars movies or books, such as Darth Vader being Luke's father or Palpatine being a Sith Lord, it is accepted as common knowledge among fans afterward, and subsequent EU products accept it as true.

But who in the Star Wars galaxy knew that Luke was the son of Vader? It seems that the reputation of Anakin Skywalker occasionally preceded him. But this is where it gets confusing: In Luke Skywalker and the Shadows of Mindor, the in-universe media propagate exaggerated and often false depictions of Luke's biography, so when Nick Rostu encounters Luke, there are a few misunderstandings that have to be cleared up. This scene hints that nobody seemed to know that Darth Vader was Anakin Skywalker, and that Anakin was the last heroic line of defense at the Jedi Temple as Vader and the 501st exterminated the Jedi. It's rather consistent of works from Revenge of the Sith to Return of the Jedi in chronology to shroud Vader in mystery, as nobody seems to know where he came from. I have a vague recollection of Tarkin speculating on Vader's origins, but not coming to a definite conclusion.

At some point, though, it must have been revealed to the whole galaxy who Vader was, probably sometime after the Battle of Endor and the formation of the New Republic. My question is whether any sources state categorically when this became common knowledge.

This question applies to some other mysteries, as well. Who knew that Palpatine was a Sith Lord? In Forces of Corruption, Tyber Zann states that "Darth Vader may be the only known Sith Lord in existence," but there are events like the Anti-Sith Conspiracy that seem to show that people knew that the Emperor was a Sith Lord as well. Did Palpatine reveal right after the Declaration of the New Order that he had knowledge of the dark side? I'd find that hard to believe. And if so, why did Tarkin say that Darth Vader was all that was left of the Jedi religion (putting aside the fact that the Emperor used several Dark Jedi as Emperor's Hands and Inquisitors).

And when was it learned that both Luke and Leia were the offspring of Darth Vader? The Noghri accept this as fact, and it is an important plot point in the Thrawn Trilogy. But in I, Jedi, Corran Horn is surprised when Luke tells him this. When did it become common knowledge that Luke Skywalker and Leia Organa were brother and sister, and the son and daughter of Lord Vader?

And what of Count Dooku? Does the public know that he's a Sith Lord? I'd expect not, but the Jedi know it, and so does Palpatine. Do the clone troopers know? And how public was the Jedi's suspicion that the enigmatic Darth Sidious was influencing the Senate? Did Dooku, for that matter, even know that Darth Sidious was planning to transform the Republic into a Galactic Empire? That Sidious was, in fact, the Chancellor of the Republic? There are hints that he's aware of a bigger scheme, but he never explicitly states that he knows his master's ultimate plan in any of the material that I have read.

Who knew what and when? - C3PO the Dragon Slayer