I wondered about the distance between the Narnian stars too. Were the stars light years away from each other and were there galaxies in the heavens above Narnia?   But of course the Narnia books are not astronomy textbooks so things do not have to be as they are in our universe.  C.S. Lewis had very little interest in math or physics. In fact he admitted that he was terrible at mathematics and it was probably a good thing that he didn’t need to do it in his literature profession.  I don’t think he would have wanted to become an astronomer even though he liked science fiction such as H. G. Wells and Jules Verne . It worked for him to have the stars as people like Ramandu and Coriakin. Lewis wrote his own fantasy such as the space trilogy, and he loved theology even though he was not a minister. So does it really matter that much if his astronomy in Narnia wasn’t completely accurate like the professional scientists?  🙂

I don't think I have ever speculated about these details.
What matters for me is what Lewis did write, to enjoy it and think about it. He created characters whose very existence amazes us, very like those in the world we live in. 
I like the star characters, though! They are interesting and different in how they are placed and described. (we may wonder why each is so different, and whether certain behaviours or experiences did that to them)

I didn't mean how many light years away the stars were, because obviously they weren't stars, but people. 🙂 I meant given that they were people, how did they work with the mechanics of the world being under a sealed dome, and a sun that was not only a sun but its own world with birds, mountains, and plant life? I get that Lewis wrote a lot of this for poetic and otherworldly effect, and wasn't looking at the larger picture, but I do speculate.

@cobalt-jade 

I wonder if there were galaxies in the skies above Narnia.  Of course the word galaxy was not even mentioned in the books as I remember.  If the stars were people and galaxies were huge collections of stars how could they live in the space above Narnia? Of course we don’t know many stars there were in the skies above Narnia or if the space was different from Earth where the star people were supposed to live.  Since the Narnia books are not astronomy textbooks Lewis was not really obligated to explain the science of that world. It’s interesting to think about though. 🙂

Did the Narnians ever use telescopes for astronomy?  I don’t remember them being mentioned in the books, although stars and constellations are referenced a few times.  There was Roonwit the centaur mentioned as a stargazer and Doctor Cornelius giving astronomy lessons to Prince Caspian. And of course Ramandu and Coriakin were stars that were people. And there is mention of different constellations in The Voyage of the Dawn Treader when the ship sailed east. As I remember in The Last Battle the end of the sun, moon, and stars is told. But did anyone in Narnia ever use a telescope for astronomy or even for navigation of ships like the Dawn Treader ?  Or did they they completely rely on naked eye viewing of the stars for sailing? The professional astronomers of Narnia would have avoided the use of too much technology. The telescope was invented on Earth in Galileo’s time, which may have been too modern for a medievalist like C. S. Lewis in creating Narnia.  I am not sure if a sextant was ever used in that world. Although something like the sextant was used by the ancient Greeks. It may have been considered by Lewis to be an invention of our modern world.  🙂

If any Narnians were mentioned as wearing spectacles or glasses, or used a magnifying glass, then I assume there were telescopes, because both used lenses.