I have been reading about rotation curves, and the I understand the basics, but I am trying to understand the basis / meaning of the curves? Are the findings based on redshifts of individual stars / "bins of light" at set distances from the centre of the galaxy? And given that the predominance of the stars / bins are at the outer "edge" of the galaxy, are there corrections to the data for this? I appreciate that these are likely "big picture" questions, and am happy to get pointers to articles / papers that can help my understanding. Thanking you in advance, Noel.