How do I get more divination quest targets to appear in the celestial globe?

It will only show a few to begin with. Keep clearing them and then tap on the Level indicator o the left to see if you can level up. The higher the level the more quests it will find for you.

There is a timer as well. So once you clear the Divination quests, in the upper right there is a timer showing when it resets and new quests appear.