I've just rewatched Star Wars Episode IV: A New Hope, and I don't recall anyone mentioning Anakin by his first name. So my question is, when did Luke learn his father's first name, and who told him it, his uncle or someone else?
Within the main film canon, the first time Luke hears the name Anakin is during Ben's "from a certain point of view, I'm not a huge liar" speech on Dagobah during 'Return of the Jedi'.
“You told me Darth Vader betrayed and murdered my father.” The bitterness he’d felt earlier, with Yoda, had found its focus now on Ben.
Ben absorbed the vitriol undefensively, then padded it with instruction. “Your father, Anakin, was seduced by the dark side of the Force—He ceased to be Anakin Skywalker, and became Darth Vader. When that happened, he betrayed everything that Anakin Skywalker believed in. The good man who was your father was destroyed. So what I told you was true … from a certain point of view.”
“A certain point of view!” Luke rasped derisively. He felt betrayed—by life more than anything else, though only poor Ben was available to take the brunt of his conflict. “Luke,” Ben spoke gently, “you’re going to find that many of the truths we cling to depend greatly on our point of view.” - Return of the Jedi - Novelisation
Note that it stands to reason that he already knew his father's name before this speech (presumably from Beru and Owen) but this is the first time that we hear Anakin's name in Luke's presence.