Comment on Banquo's speech beginning “There's husbandry in heaven...” and ending “...in repose”.
Remember that this play would originally have been performed in the daytime, using natural light.
You raise an interesting question. How can Banquo claim to be looking up at the night sky when the play is being performed in broad daylight? Shakespeare seemed to care little about authenticity in stage settings. The opening lines of this scene are intended to establish that it is after midnight, and the audience is supposed to imagine it as such. The torch that Fleance is carrying is the only prop. Shakespeare frequently used dialogue between characters to convey information to his audience. Even today Shakespeare’s plays are often performed in the open air in public parks in the day time. If this scene from Macbeth were being performed in daylight in such a place, the audience would just have to understand that it was nighttime.
A lot happens in this very short scene. Banquo confesses that he cannot sleep because he is tormented with thoughts which must have been evoked by the meeting with the Weird Sisters. Time is of the essence. It has to be nighttime because the King must be asleep. Banquo meets Macbeth and they talk in hushed voices in guarded language. Macbeth subtly sounds Banquo out about participating in a bloody coup. Banquo turns him down flatly, saying, “So I lose none [honor] / In seeking to augment it, but still keep / My bosom franchised and allegiance clear, / I shall be counseled.”
Macbeth has to commit the murder alone. The scene ends with him headed for Duncan’s chamber with a dagger. No doubt he would have preferred to kill Duncan’s two sons the same night but thought he needed help. All this happens in just a few pages. It must be in the dead of night when everyone else is asleep.