His subsequent main astronomical works were in some sense only further developments of it, concerned with finding more precise inner and outer dimensions for the spheres by calculating the eccentricities of the planetary orbits within it.
Hans senere, centrale astronomiske værker blev på nogle måder blot en yderligere udvikling af den, interesseret i at finde mere præcise indre og ydre dimensioner for sfærerne ved at beregne excentriciteterne af de planetariske kredsløb inde i dem.