Catalogo di 1321 stelle doppie

misurate col grande equatoriale di Merz all’Osservatorio del Collegio Romano e confrontate con le misure anteriori
Angelo Secchi
Roma, Tipografia delle Belle Arti, 1860
[pag. 9]
220 x 290 mm
Library of INAF- Arcetri Astrophysical Observatory, Florence

The record of measurements of double stars made by Father Angelo Secchi contains the measurements made on that class of objects since 1855 to 1859 with the Merz telescope of the Observatory of the Roman College. A total of 2769 measurements of 1321 binary and triple systems, most of which belonging to the record Mensurae Micrometricae di Friedrich Georg Wilhelm Struve. Research about those object was indeed carried on in a systematical way by the famous Prussian astronomer, who started the work at the Observatory of Dorpat (Tartu) and then published his observations in 1837 in S.Petersbourgh, in the above mentioned issue, work that constitued for more than a century a true vademecum for all the astronomers who made this kind of observations.
Father Secchi’s purposes himself to observe again all those binary stars showing a significative motion, to better investigate their orbits, where possible, and to confirm or debunk the orbital motion for uncertain cases. The study of binary systems will be, together with the first spectroscopic star observations, an important step for the transition from classic astronomy toward the new fronteer of the modern astrophysics. While spectroscopy gave the first informations about the composition of the stellar atmosphers at that time, research on binary stars provided informations about the dynamics of the systems outside the solar system, area of interest in which the conjectures and the calculations of the “classical” astronomer were enclosed. Thanks to the knowledge of the orbit of a binary star was indeed possible to obtain data on the distance, the sum of the masses, and in some cases even the masses of each star- impossible to obtain by other ways- or, assuming a statistic value for that parameter, obtain “dynamic parallaxes”, a statistical information about the distances of those objects, in a period in which the determination of trigonometric parallaxes were an absolute rarity and extremely difficult to compute.
For the first time the astronomers had a medium to investigate the distribution of the stars of our Galaxy, thing of which Father Secchi was well aware of. In the record a lot of space is devoted to the confrontation of his observations with Struve’s ones, and the observations of previous and contemporary astronomers to highlight the orbital motion whenever possible. The only flaw of the record could be the fact that Secchi kept the distribution of the stars in the same orders of distance of Struve for the organization of the measurements, rather than applying the organization for crescent straight ascension criterion, who would made the consultation simpler; however it is only a formal flaw, surely inspired by the authority of the famous astronomer from Dorpat, respected also by the modern astronomers.
The page here depicted shows the data of one of the most known binary star with known orbital motion, the Gamma of the Virgin, which Secchi repeatedly observed, aiming for the maximum precision. The page is located in the section showing the classification of the I-V orders of Struve, with the distinction among the stars Lucidae e Reliquae that is the main body of the record (pp.5-112); afterwards there is an appendix with vaorious stars with the most separated orders of Struve(pp.113-115) and other catalogues(pp.116-118); finally, a resuming panel in which the observed stars are ordered afte their classification of their motion.

Giuseppe Massone - INAF-Osservatorio Astrofisico di Torino