How can i get to celestix town in pokemon diamond?

Also, where can i find Cynthia in pokemond diamond? (for the side ducks)|||First of all, its Psyducks. Second of all, you need to get rid of them to get to Ceelestic town. First you go to Valor lake front, and you will find her. She will give you and Something potion i cant remember the name. Then you give it to the psyducks, and then go through the route and then go to the town