You apparently missed the fact that Sarah is pretending to be two different people.  First, during the inspection of the Everest and dinner party, she changed her appearance to what it had been like 30 years ago, when Jason last met her... and apparently, Jason only knew her as "Aunt Yseriac".<br/><br/>Aunt Yseriac claimed to be a engine tech or something along those lines, and asked for everyone else to play along with her...<br/><br/>NOW she's dressed up as the fictional version of "Voidmistress Sarah" from the movie, and is pretending to be... a different version of herself.<br/><br/>And yes, apparently Captain Harlock is clueless.  (mainly because Tagan asked nicely...)  Apparently he only knew her for short periods, and for some reason doesn't know Sarah's first name, despite her being his godmother.... and he's never bothered to find out what her first name is... or what the last name of one of the Captains in the very small fleet he's serving in?<br/><br/>Yeah... plausibility is stretching a bit thin there... but Tagan did ask nicely.