I need help on a quest where I have to go to the Cosmodrone and I have to defeat 3 Taken champions (not the quest that I had to do for Petra). And I have to defeat the following: Ixori, Lost to Oryx Stirok, Banner of Oryx Darnu, Horn of Oryx I know I have to go to the Skywatch in order to defeat them, but I don't know how long to wait for the Taken to arrive.