The reconstruction of the historical archive of the Arcetri Astrophysical Observatory followed a rather complex and articulated path, involving recoveries and acquisitions.
During the 1990s, following renovation work on the Library and several rooms of the Observatory, folders containing various types of documentary material (letters, article drafts, manuscripts, observation reports, etc.) were discovered. These documents immediately revealed their historical value. There were 31 containers in total, some relating to the more recent history of the institution and others to the activities of Antonio and Giorgio Abetti, who served as directors of the Observatory from 1894 to 1922 and from 1922 to 1953, respectively. Particularly noteworthy among this collection are the letters from George Ellery Hale to Giorgio Abetti concerning the construction of the solar tower, as well as numerous documents related to observational activities. In the months that followed, additional administrative and accounting documents were found in other parts of the Observatory.
In 1998, the Archival Superintendency for Tuscany carried out several inspections to assess the extent of the collection, immediately recognizing its considerable historical significance. In 2003, thanks to the collaboration of the Institute and Museum of the History of Science in Florence, what were believed to be all of the Observatory’s ancient records were recovered. This included a rich set of documents belonging to the Antonio Abetti collection, as well as several folders of correspondence related to the De Filippi expedition to Karakorum in 1913–1914. Furthermore, in the spring of 2007, the Institute and Museum of the History of Science discovered additional material related to the Observatory. After several inspections confirmed this connection, the materials were acquired. The find included around 60 items—envelopes, registers, and bundles—some of which contained the oldest observations, dating back to the period when the Observatory was still located in the tower, the “Specola,” of Palazzo Torrigiani on Via Romana.
An additional acquisition took place in 2006, when a number of documents connected to Giovan Battista Donati were purchased from an American antiquarian. These letters, sent to Donati by eminent Italian and foreign scientists such as Le Verrier, Secchi, Tacchini, Schiaparelli, Delaunay, and others, cover the period from 1854 to 1872. This collection confirms the network of international relations that G.B. Donati had cultivated, particularly for organizing observation campaigns of specific astronomical events. A testament to this is the wealth of documentation related to the 1872 aurora borealis, which reveals correspondences from across all latitudes of the globe.
In 2012, during maintenance work on some of the Observatory’s rooms, additional scientific and administrative papers were discovered.
Completing the picture is a valuable "rediscovery" within the Observatory: a folder containing about 130 letters from Father Angelo Secchi to Pietro Tacchini (1865–1877), donated in 1939 by Tacchini's grandson to Giorgio Abetti.