I had accidentally edited your post instead of creating a new one. I restored your comment.
I don't think I said that observation was the only thing astronomers did, just that the observation was a big part.
During the 20th century, the field of professional astronomy split into observational and theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, which is then analyzed using basic principles of physics. Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the observational results and observations being used to confirm theoretical results.
Astronomers were certainly not putting the universe under controlled conditions when coming up with their theories. Chemists can put their subject matter under controlled experimentation to come to the truth of a matter. Astronomers cannot. That is why Chemistry is a science and why Astronomy is not.
It is said that Astronomy is an "observing science," but an observing science is not really a science at all. We need actual experiments that demonstrate theories to be true. Otherwise they are just stories, no different than the stories African tribes have for the nature of the stars above them.