Are the solar systems depicted in Larry Niven's fictional book series about "Known Space" based on observations from Earth? Or, once the story leaves our solar system, does his science fiction lean more towards fiction than it does to science?
As can be seen from the Wikipedia article, there is plenty of real stars among the stars mentioned in Known Space. While no doubt some of the further out ones are not real world stars, the closer ones tend to be spot on.
Of course, there are no known planets at any of those stars that I'm aware of, and certainly none matching the descriptions. Known space has been around much longer than our knowledge of any planets.
Most of Larry Nivens' Known Space stories were written before the first discovery of a real extrasolar planet in 1988, so they are truly science fiction.