In December 1773, he moved to Ravenna, where he served as "prefetto degli studenti" and as a lecturer in Philosophy and Mathematics at the Collegio dei Nobili, a position he held until early 1779.

Almost at the same time, he was granted permission to spend two years in Paris and London, to undergo some practical training in astronomy and also to get some instruments to be specially built for the Palermo Observatory, whose foundation he was in charge of.

In the period spent abroad, from 13 March 1787 until the end of 1789, Piazzi became acquainted with the major French and English astronomers of his time and was able to have the famous altazimuthal circle made by Jesse Ramsden, one of the most skilled instrument-makers of the 18th century.

[4] Spurred by the success discovering Ceres (see below), and in the line of his catalogue program, Piazzi studied the proper motions of stars to find parallax measurement candidates.

In his journal, he wrote: The light was a little faint, and of the colour of Jupiter, but similar to many others which generally are reckoned of the eighth magnitude.

Nevertheless before I made it known, I waited till the evening of the fourth, when I had the satisfaction to see it had moved at the same rate as on the preceding days.In spite of his assumption that it was a planet, he took the conservative route and announced it as a comet.

Piazzi named it "Ceres Ferdinandea," after the Roman and Sicilian goddess of grain and King Ferdinand IV of Naples and Sicily.

More recently, a large albedo feature, probably a crater, imaged by the Hubble Space Telescope on Ceres, has been informally named Piazzi.