Complex sentence: For the most part Hergé's research is evident in this book, but he (deliberately or not) missed the fact that the Inca were experienced astronomers, who would have been able to predict a solar eclipse almost as well as any modern scientist.
Split into simpler sentences: For the most part Hergé's research is well-reflected in this book, but he (deliberately or not) missed the crucial fact that the Inca were experienced astronomers. In real life, the Inca would have been able to predict a solar eclipse almost as well as any modern scientist.