You go to the lake near your character's home town (Where is Mesprit) and you will see the professor and your girlfriend battling. You help them and you go to the lake where is Uxie. You beat them all then beat the gym leader. Then you go to the Spear Pillar and catch Palka/Diagla/Girratina.
Read more: http://wiki.answers.com/What_do_you_do_after_beating_commander_Saturn_in_Pokemon#ixzz16YMhObWz
Chat with our AI personalities
No. You need to beat the Pokemon League IN the Platinum one.
nothing
On Pokèmon Platinum, you get the Dowsing Machine after you beat the Sinnoh Pokèdex, when you talk to the Professor.
well i have beat them in Pokemon diamond and u have to gust cheap on trying to beat them
fly