The gravitational influence of Jupiter on Saturn produces, among other things, non-negligible changes in the eccentricity of Saturn that affect the magnitude of error of Ptolemaic astronomy. The value that Ptolemy obtained for the eccentricity of Saturn is a good approximation of the real eccentricity—including the perturbation of Jupiter—that Saturn had during the time of Ptolemy's planetary observations or a bit earlier. Therefore, it seems more probable that the observations used for obtaining the eccentricity of Saturn were done near Ptolemy’s time, and rather unlikely earlier than the first century AD. Even if this is not quite a demonstration that Ptolemy used observations of his own, my argument increases its probability and practically discards the idea that Ptolemy borrowed values or observations from astronomers further back than the first century AD, such as Hipparchus or the Babylonians.

中文翻译：

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木星的引力对土星偏心率的托勒密值的影响

木星对土星的引力影响导致土星偏心率发生不可忽视的变化，影响托勒密天文学的误差幅度。托勒密获得的土星偏心率值很好地近似了真实的偏心率——包括木星的扰动——土星在托勒密行星观测期间或更早的时候所具有的。因此，用于获得土星偏心率的观测似乎更有可能是在托勒密时代附近完成的，而且不太可能早于公元一世纪。即使这不能完全证明托勒密使用了他自己的观察，