A researcher at the University of Limerick has uncovered a previously unknown 17th-century manuscript that provides a component-by-component technical description of a four-lens terrestrial telescope attributed directly to the Italian astronomer Galileo Galilei.

Dr. José María Moreno Madrid, a scholar at the university's School of History and Geography, identified the document while analyzing a 1666 manuscript titled 'De Tellescopiis Stellarum' written by Spanish Dominican friar Ignacio Muñoz. In the text, Muñoz provides optical measurements and structural details of a four-lens telescope, describing the instrument in Latin as 'fabricatum a Galilaeo'—manufactured by Galileo.

The research, published in the peer-reviewed journal Annals of Science, could alter existing historical timelines regarding early optical technology. Prior historical records dated the emergence of four-lens terrestrial telescopes to between 1643 and 1645, with widespread European production establishing itself in the second half of the 17th century.

According to the manuscript, the telescope was presented to Muñoz by Antonio Sebastián de Toledo Molina y Salazar, the Marquis of Mancera and then-Viceroy of New Spain. Historical records record that Galileo had previously presented telescopes to King Philip IV of Spain in an effort to secure royal backing for solving the problem of calculating longitude at sea. Dr. Moreno Madrid suggests the telescope detailed by Muñoz may have reached the Marquis de Mancera as a diplomatic gift from the Spanish court.

Dr. Moreno Madrid stated that if the manuscript's attribution is correct, known experimentation with four-lens telescopes would be pushed back to 1630 at the latest and credited to Galileo. He noted that even if the attribution were to be challenged, Muñoz's document remains an important technical record expanding knowledge of 17th-century telescope construction and early modern scientific exchange.