The astronomical instruments of Santa Maria Novella
Between 1572 and 1575, the cosmographer Egnazio Danti (1536-1586) installed on the façade of Santa Maria Novella no less than three astronomical instruments: a great quadrant with sundials, an equinoctial armillary, and two "camera obscura" gnomons. These instruments were designed to be used for new astronomical calculations linked to the project for reforming the Julian calendar, which would have definitively re-established the exact liturgical date of Easter and the related movable feast days. Danti was convinced that the problems of the day relevant to the calendar were so complicated as to call for an overall revision of what was known of the sun's movements. Favoured by the patronage of Cosimo I de’ Medici, a supporter of the reform project subsequently implemented by Pope Gregory XIII, Danti spent the last years of his stay in Florence constructing astronomical monuments. Although these gnomons were designed in 1575, Danti was unable to complete the tracing of the meridian line on the floor of the church. He only opened gnomonic holes, first in the glass of the rose window, then on the church's façade, much higher, and made two openings in the vaulting as well, through which rays of light would pass only during the equinoxes and the winter solstice.