This 15th century manuscript is a copy of an astronomical text known as the Theorica Planetarum, which was incredibly popular in the medieval period, and survives in over 200 manuscript copies. There has been much debate on the authorship of this text, and it has been attributed to Robert Grosseteste, and also Gerard of Cremona. However, it seems most likely that this text, of which MS 128 is a copy, is the work of an anonymous teacher of astronomy from about the mid-13th century. Given the apparent popularity of this particular text, evidenced by its supplementary inclusion in Sacrobosco's works that had become established as the core of the 13th-century astronomical curriculum, this Theorica Planetarum most likely was written shortly after the mid-13th century in a place where Sacrobosco's texts had already risen to prominence in the field of astronomy.

The text starts on f. 1r with the following words: Circulus ecentricus vel egresse cuspidis, and ends with: bicubitum vel tricubitum vel majoris quantitatis. Explicit theorica planetarum. Finis. on f. 14v.

Very fine italic script.

Rubrics of Roman capitals in red, and one good burnished gold initial with vine-leaf scroll.