re: Question about Eta Carinae
Eta Carina had been observed in 1841 as being for a short while the most brilliant object in the sky. Then it faded and it returned back in the news thanks to the HST but I'm not aware of a time lapse (there are pictures of Eta Carina taken by the HST where differences are noticeable, but not like the star in Monoceros).
Raoul