https://www.youtube.com/@JasonKendallAstronomer
I like Jason Kendall's online astronomy course which evolved from his years teaching undergrads. There are about 15 "modules" of some 3 hours each. First few modules are elementary and a quick review. Middle of the sequence gets into much deeper end of the pool.
His great slides emphasize the physics behind what we see: lots of example photos, graphs, spectra, basic equations. Also I found this course a fascinating history of astronomy, which, IMHO, is the history of physics.
Kendall's videos at this writing appear to be continually updated and expanded. Sometimes it's tricky to keep track of the links when trying to view the modules in sequence.... basically due to the huge amount of material here.
