I don’t know how I would describe it. I just don’t like imagining myself feeling extremely small compared to the universe on the outside. I don’t like being anywhere where I can’t breathe air, so I would not be an astronaut. I can look at space pictures and stars fine, as long as they are images and DON’T show the scale of the whole thing.
I don’t think it is astrophobia, because I like looking at the stars and stuff, I just don’t like the idea of something being so large it has no end.