Realising that he had not long to live he devoted his last months to completing his major work on The Motion of the Moon which he completed shortly before his death:
Realising na niya na hindi mahaba buhay na siya sa tapat ng kanyang huling buwan upang makumpleto ang kanyang trabaho sa mga malalaking Ang Motion of the Moon na kung saan siya natapos sa ilang sandali bago ang kanyang kamatayan: