Be ready to pay 60 USD to access the textbook and hw for a quarter. There are 3 online HW due dates per week and a mandatory in-class essay administered during sections each week. The exams are entirely MCQs so it is very easy to get thrown to B-. Lectures are fine but don't provide sufficient insight. Just take someone else's class...

Great professors, but the exams you need to take are harder than the assignments and harder to get a grade for.

This has been one of my favorite classes due to both material and professor. Geller is great and I loved the lectures. Tests were kind of hard, but weren't weighted very heavily (final = 20%). There is kind of a lot of homework, but it was generally pretty easy and didn't take long. Doing/understanding homework is necessary for good grade.

Only chance to ask questions is in lecture. He is responsive and helpful, but you're expected to rely on TAs for info outside of class. Lots of homework and reading per week. Lots of studying is recommended, you cannot just do the bare minimum in this class. Grading is dominated by your homework and quizzes but includes long midterms and finals.

In terms of difficulty, his class was not free, but I think if you put in the effort, you can get a decent grade. For his lectures, I attended every single one because they were so fun. He is clearly very passionate about what he teaches, and that passion is very contagious. I would suggest you do a quick review before the discussion sections.

The online version of Astro 1 is a blend of easy mathematics (Usually the hardest math being like AP Physics 1 level), really interesting concepts, and such. Expect to read a LOT for the online version of the class but it isn't hard at all. Great for a STEM elective, just okay for a STEM GE.