It cannot be caught either diamond or pearl. The only way to obtain it is to catch it in Pokemon Colosseum, trade it to a GBA game, and transfer it to diamond and pearl.
Here are the instructions for getting Ho-Oh
http://www.serebii.net/colosseum/ho-oh.shtml
you catch it in a gba game then catch it in the palpark
www.serebii.net
You cannot catch rayquaza in diamond
to catch any of these u need either a gameshark or use other cheats.
Catch suckish Pokemon and lose every battle.
You can't unless you trade with somebody. Anyways Moltres is better
You don't t catch them D/P it has 2 B transfered from Sapphire,Ruby,Emerald
i know how to catch regigiigas he is at the bottom of snow point city temple but i don't know how to catch the rest sorry cant be of further use
I think you have to transfur from ruby version or something, I havent done it yet.
you need to do mean look and then yust throw balls
The only way I'm familiar with besides the Action Replay is to catch it in Leafgreen or FireRed and then migrate it.
Sorry to burst your bubble, but you can't. You should trade it from a Pokemon Pearl or Platinum game.