Astrolabe: dismounted reverse

The appearance of this astrolabe is crude and quite unlike what one might expect from an Italian object of 1568. The engraving is of poor quality and the calendar on the back is not accurately divided or numbered. Thus, the authenticity of this instrument is questionable. It appears that the different parts of this astrolabe are brass reconstructions of the illustrations from Danti's book 'Dell'Uso et Fabrica dell' Astrolabio', published in Florence (1578). Therefore, it could be that the plates were made for usage in a classroom or some other educational context - to be used in conjunction with the diagrams in the book. There is a twin instrument in the Naval Museum at Genoa.

The throne comprises a long, thin brass strip that is soldered on to the curved rim. At the centre is a simple base that is pierced on the top for holding a (now-lost) suspension ring. The Mater consists of a brass plate covering a wooden core. There are three plates, each side engraved with a series of diagrams that show the different stages in the construction of a traditional plate with a stereographic projection. On the back of the instrument is a combined scale for degrees and the zodiac and a calendar scale. In the lower half of the remainder of the back is a shadow square, inside of which is an inscription dedicating the astrolabe to Ferdinando de Medici and also giving the maker as 'Egnatio Danti' in the year 1569.
Egnatio Danti