"Where is the moon tonight?"
Translation:आज रात चाँद कहाँ है?
I was wondering also if there is an "invisible" को that should be accepted.
रात को means "nights, at night".
आज रात means "tonight".
आज रात को आठ बजे means "at eight o'clock tonight" (but note that it's in the near future in that phrase).
But maybe if it's already night, and we're wondering where the moon is right now, को does not make sense anymore?