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Fig. 19.3 Photograph of the Ertel meridian circle at Campidoglio Observatory (datable around
1900; INAF-OAR, historical archive); the instrument was provided to Ignazio Calandrelli by Pope
Pius IX in 1849. Today the Ertel meridian circle is kept in the collections of the Astronomical and
Copernican Museum at INAF-OAR
19 Astronomy in Rome After Secchi and His Legacy at the Astronomical Observatory…