You can view the clock for free anytime the Cathedral is open, but if you want see all the…read moremovements of the animated characters, there is a video presentation that starts at noon, with the clock moving at 12:30 pm. There is a nominal charge, which will make sense to you later if you are in the area around the clock with 400 people, only so many people can fit
The video is excellent, and is presented in French, German, and English.
The clock itself is a treasured masterpiece of clock-making, astronomy, and mathematics. The storytelling is very good, as well.