How To Catch Latos And Latias Without A Masterball:

first you need find one of them when you find it go straight to mauville city and by 15 ultra balls and ten max repels then go to the hunters house and keep going in and out of his and look at yopur pokedex and see what route its in when its in your route use a repel and mak sure you have wynaut or a wobaffet at the front of your party on a high level (lv 45) and attack it until its on red healyh and keep using your ultrs balls on it and youll adventually catch it