OK, I'll bite.
Caelumviator seems to sound very Latin...
Google Translate gives us: Caelum=Sky; Viator=Traveler.
If that wasn't a Latin translation of "Skywalker", I'm going to eat my honorary SciFi.SE Latin Google badge (Hint to SE team: I want that badge!)
Since the actual details of the plot in the question seem to match (2 robots, R2-D2 and C-3PO seek their owner, Obi-Wan Kenobi, to deliver the Death Star plans to him so he can send them to rebels on Aldaraan - and obviously there is a big space battle in the end), the book you read must have been novelization of none other than "Star Wars":
The Star Wars Episode IV: A New Hope novelization, originally entitled Star Wars: From the Adventures of Luke Skywalker, was the official novel adaptation of the film Star Wars Episode IV: A New Hope, published in 1976 by Ballantine Books. It was ghostwritten by Alan Dean Foster, but credited to George Lucas.
The actual answer to your question (who was the author) is bolded by me above
An additional factor confirming this was, of course, the mention of the owner being a Samurai - it is a well known fact that George Lucas acknowledged a strong influence of "Hidden Fortress", one of the classic Samurai movies, on "Star Wars: A New Hope".