These showed his excellent abilities as an observer and he made impressive contributions with his study of the moons of Jupiter and Saturn and his study of the structure of Saturn's rings. Most notable of his discoveries was that of the proper motions of the stars which he made in 1738.
Ang mga ito ay nagpakita ng kanyang kakayahan bilang isang mahusay na tagapagmasid at siya ginawa kahanga-kontribusyon sa kanyang pag-aaral ng Buwan ng Jupiter at Saturn at ang kanyang pag-aaral ng mga istraktura ng Saturn's rings. Pinaka-tanyag ng kanyang mga discoveries ay na ng tamang motions ng mga bituin na kung saan ginawa niya sa 1738.