The 25 cm diameter Merz telescope, installed in 1854, was the most important instrument of the new observatory of the Collegio Romano made by Secchi. It was purchased to compensate for the lack of a modern equatorial-mount instrument, and was one of the best telescopes in the astronomical observatories of the time and one of the largest in Italy. The funds to buy the Merz came from a legacy inherited by one of the assistants of Secchi, Paolo Rosa, of the family of the Counts Rosa Antonisi. The use of this instrument produced an immediate leap in the quality of the studies carried out by Secchi and his collaborators at the Collegio Romano. It was also used for the first stellar spectroscopic observations performed at the Observatory and it greatly contributed to the development of solar physics, thanks to the comparison with the results obtained in Palermo with an almost identical Merz telescope, used by Pietro Tacchini. The telescope remained in use at the observatory of the Roman College until 1889, when it was transferred to the annexed Astronomical and Copernican Museum, wanted by Tacchini. Following the transfer of the museum, in 1923 it was transported to the new observatory of Rome on Monte Mario; It was then inappropriately used in the Fifties as a seeker of a modern Steinheil telescope. Both telescopes were destroyed by a fire in 1958, so that nothing remains of this glorious instrument, except the granite pillar on which it was mounted, remained in the unsafe premises of the Roman College, awaiting a near restoration of the whole complex.
A. Altamore, F. Poppi, S. Maffeo, “Merz Telescopes in Rome” in: I. Chinnici (ed.) Merz Telescopes, Springer, 2017