One thing explorers were looking for on their voyages was?

Land, Gold, and other forms of valuables, but land for their country was also very important. For example, Columbus returned with new land and many valuables back to Spain. And Cortes was seeking gold and found plenty in his conquering of the Aztecs. 

I would say the new moon because you don't get any moonlight because the moon looks non-existant. Any other phase would be okay because there is some moonlight coming from the moon.

I Hope This Helps You Out!!