This is a diagram of how a solar eclipse works, or at least how they thought one worked in the 14th century. It might be one of the very first illustrations of its kind. As explained by the book’s description in archive.org:
This book, which contains Sacro Bosco’s influential, 13th-century astronomy tract, along with works by Peurbach and Regiomontanus, is notable for its color illustrations. In particular, this edition, issued by Erhard Ratdolt in 1485, is considered to be the first book printed with multi-color illustration.
If you want to see more eclipse art through history, I recommend this Atlantic article from September 2016.