After approximately 40 failed attempts, in early 1605 he at last hit upon the idea of an ellipse, which he had previously assumed to be too simple a solution for earlier astronomers to have overlooked.
Efter omkring 40 forgæves forsøg kom han først i 1605 på ideen om en ellipse, som han tidligere havde antaget som en for simpel løsning til, at tidligere astronomer ville have overset den.