Can the Sun Nakshatra be used for Tara Tables?

Hello!

I apologize if this is a dumb question, but I like to look at the signs of fictional characters to see if astrology applies to their personalities, but often I find that even when given a birthday, if they're from some fictional land it makes it impossible to find any other placement outside of their sun rasi & (maybe) nakshatra. For that reason, I was wondering if making a tara table for their relationships with other characters would be a waste of time or not.

Thank you!

JM