Ignazio Calandrelli (22 November 1792 – 12 February 1866) was an Italian priest and observational astronomer.
He studied theology and joined the Gregorian University, receiving a degree in philosophy in 1814 when he became a student of his uncle at the Collegio Romano observatory.
He was then appointed professor of elementary mathematics and then taught at the Saint Apollinare seminary.
A Merz achromatic telescope (11.4–cm [9”] aperture, 190–cm focal length) was donated to the observatory by Marquis Giuseppe Ferrajoli (1798–1870) in 1869.
[1] He published observations on the movements of planets and comets in the proceedings of the Accademia dei Nuovi Lincei.