I liked this course. It presented difficult fact in an engaging manner. I'm giving it 4/5 because the lectures were taped from live lectures, rather than prepared for the course itself, and that makes the most of the students questions inaudible. The assignments were nice, and the level of engagement was nice as well. It's now an archived course on edX and a self-paced one on Coursera, so check it out. Watch out, there are no more certificates available. Be sure to check out Galaxies & Cosmology after this course and to take this one prior to G&C, since you could end up confused in the latter because it's quite an advanced course. The professor is engaged in the forums, and responds to inquiries, so that's a huge plus.