The pieces of implicit evidence that support the analysis that William is already very knowledgeable about astronomy when the story begins are:
- He knows that his work mapping the constellations has already been done.
- He owns his own telescope.
- He knows that he requires more training to become a professional astronomer.
- He takes notes without having to look at his journal.
All of these options suggest that William has a strong foundation in astronomy and is actively engaged in the subject.