Here's the order after Heatran:
1. Cresselia (Fullmoon Island): You can encounter Cresselia after defeating Heatran in the Stark Mountain area.
2. Giratina (Turnback Cave): After obtaining the Azure Flute, you can challenge Giratina in Turnback Cave.
3. Regigigas (Snowpoint Temple): You can encounter Regigigas after defeating Giratina in the Turnback Cave.
4. Dialga/Palkia (Spear Pillar): The final encounter in the game is against either Dialga or Palkia, depending on whether you have Brilliant Diamond or Shining Pearl.
Important Note: The order of the Legendary encounters can be slightly altered based on your choices and progress in the game. For example, you could encounter Cresselia before completing the main story, but you would still need the Azure Flute to access Giratina.