1)Buy 50 ultra and timer balls. 2)Go get a level 50+ aggron. 3)Go to Rayquaza and engage battle. 4)DON'T ATTACK, JUST HEAL 5)Eventually, it'll use rest. During that time, pummel him with ULTRA BALLS. 6)When he wakes up (if you didn't catch it) repeat steps 4&5 over 2 times. 7)Use the timer balls now. If Aggron gets low, heal up with a hyper potion. 8)The timer balls will catch it, because by now the battle has been going on for 30+ turns. After about 20-30, Rayquaza will be caught.