A pilot, in marine terms, is someone who leads other boats through dangerous waters. As later chapters explain, the head of the Knysna River (where the river meets the sea) is full of rocky water, and so it’s Mr. Benn’s responsibility to try to keep these ships safe. Seeing the stars helps Benjamin realize how sheltered his life in the Forest has been—literally and figuratively, and especially compared to the wide-open environment of his early childhood.