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Speaker |
Sigismondi, Costantino |
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Coauthors |
Pietroni, Silvia |
| Talk Title |
Angelo Secchi, Gnomonics, and the equation of time during the centuries |
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Abstract |
Angelo Secchi, following the tradition started with father Christopher Clavius (1535-1612) who wrote a mathematical treatise (1581) on Gnomonics, realized sundials and quadrants. The equation of time determines the difference between the mean solar noon and the true one. Graphically it is represented with an analemma, drawn also in the sundials made by Secchi (e.g. the ones of Grottaferrata and Augusta). The relationship between the day of the year and the corresponding equation of time, from Ptolemy to Clavius, is presented, including some medieval cases. Computation methods of the equation of time based on linear interpolation of trigonometrical functions are simulated for some historical cases before Clavius. In the same years of Secchi, the parish priest Giuseppe Sarto (1835-1914), future pope Pius X, was making sundials in Veneto and later told a joke about the equation of time when he was Pope. |
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