Well that was a whole other topic. And luckily it links to a page that explains the whole topic of what a "celestial sphere" is. Going to the page, I see I was indeed wrong about what it was, but now I see it is an abstract sphere, with a radius that can be whatever size you want, and that is centered on the Earth, or on the observer.

Once again, not so difficult to figure out even if you have no experience in the specific technical field of a Wikipedia article. So I have no idea what /u/casenmgreen's problem is.