Here, catch rates are much simpler. Instead of the overcomplicated equation that is pokemon, we're making a system out of it. Simply put, if the opposing pokemon is below a certain amount of health, it can be caught without fail.
Pokeball: Below 5HP
Greatball: Below 15HP
Ultraball: Below 25HP
Masterball: 100% catch rate
Note that all legendaries can be caught, and the ones that can, can ONLY be caught with masterballs. Also note that no pokemon can have more than 300HP