At the center of the room stands the crown jewel of the Specola's museum collection: the magnificent altazimuth telescope with circular staircase, crafted in 1789 in London by the skilled English instrument maker Jesse Ramsden. The Circle was commissioned by Piazzi during his extended educational journey prior to the founding of the Palermo Observatory. Even at the time, it was considered an exceptional instrument and a masterpiece of precision mechanics. It was originally accompanied by a rotating copper dome with an openable segment, also designed by Ramsden.
With this instrument, Piazzi launched his ambitious scientific program, which culminated in the creation of a monumental star catalog listing the positions of over 7,000 stars. Published in 1803 and updated in 1814, the catalog earned him the prestigious prize of the French Academy of Sciences.
It was during an observation session with the Circle that Piazzi discovered the first asteroid—now classified as a dwarf planet—on the night of January 1st, 1801. He named it Ceres, adding the now-lost epithet Ferdinandea. This discovery brought Piazzi international scientific acclaim and elevated the young Palermo Observatory to the status of one of the leading astronomical centers of the time.
