The catch rate for Rayquaza is 3, which means that there's a 0,4% chance of catching it at full health with a normal Poké Ball. Times that with 2, since an Ultra Ball is double as effective as a Poké Ball, and it becomes 0,8% chance of catching Rayquaza at full health with an Ultra Ball. Also, congrats on the PokéRus, that shit is insanely rare.
Also, I'm willing to bet 10 bucks that when the Panda's evolution is revealed everyone will hate it.