Dear friends, a new issue of the Italian magazine Orologi Solari is available for download from the usual site http://www.orologisolari.eu/.
Here is the list of articles together with a short abstract: 1. - "Shadow and penumbra in the obelisk of Augustus" by Paolo Albéri Auber First of all, the study clarifies the reason why penumbra is missing in the perspective drawing related to the obelisk of Augustus, proposed by the author in the Pontifical Roman Academy of Archeology 2011/12 and later. More interesting is the question of the negative judgment about the penumbra (impossibility to read the position of the shadow) proposed by a British scholar (Peter Heslin), a judgment which is contested here with an accurate technical analysis and the comparison with a photography. 2. - "The mortar board sundial: the square hat sundial" by Riccardo Anselmi The article deals with hat sundials including a square hat sundial. 3. - "The sundial on a flat surface in Pierre De Flovtrieres' <Traittè d'Horologeographie>” by Alessandro Gunella The author translates and comments on a 'new' method, which the mathematician Pierre De Flovtrieres proposes in his Traittè d'Horologeographie of 1619, useful for plotting sundials on any plane, without knowing the latitude of the place, the declination and the inclination of the wall. 4. - "The Persian al-Biruni, astronomer and mathematician" by Michele T. Mazzucato The life and works of al-Biruni, one of the most famous Persian scholars, are presented. Polyglot, considered the father of Indology, he treated mathematics, astronomy, geography, physics, medicine with originality of method and research. He also devised a new method, of the trigonometric type, for determining the dimensions of the Earth by knowing the height of a mountain and measuring the angle of depression of the horizon. He used that method for verifying the results obtained by al-Ma’mūn’s astronomers two centuries earlier. 5. - "The fourth book of <The Gnomonics with ruler and compass>" by Orologi Solari editorial staff Alessandro Gunella donates the readers of Orologi Solari the fourth Book of "Gnomonics with ruler and compass", where with his unique geometric approach, he deals with and illustrates innovations and variations, partly already proposed also in this magazine, studied by him in recent years. 6. - "Story of a failed complex gnomonic dedicated to Angelo Secchi" by Renzo Righi The proposal for a gnomonic project dedicated to the memory of Father Angelo Secchi S.J., developed by the gnomonist Renzo Righi and the artist Maria Luisa Montanari, concerning the cylindrical radar tower of Gattatico (RE), is illustrated. Unfortunately the project had no follow up and in its place a work was created dedicated to the seven Cervi brothers, martyrs of the resistance, whose birthplace transformed into a museum is located nearby. 7. - "The relocation of a sundial" by Fabio Savian The author shows how with spherical trigonometry it is possible to find all the parameters necessary to relocate a sundial to a place other than that for which it was designed, while preserving the correctness of its indications, even modifying the reference meridian. 8. - "Ring sundials" by Elsa Stocco With the support of Geogebra, the construction of solar rings, portable altitude sundials of little luck, is again proposed, suggesting various hypotheses for the 'correction' of almost conscious errors made in the past in the definition of the hour layout. 9. - "Observations on the same sundial, in the texts of Fineo and Munster (short contribution)" by Alessandro Gunella The author proposes, limited to the illustration of the lines of the common hours, the correct representation in plan of a sundial, drawn on the surface of a hollow sphere by both authors. He only uses the analemma. 10. - "Welder's sundial (short contribution)" by Stefano Paris The article describes the practical realization of a small cylindrical sundial with a retractable gnomon, obtained from an unusual bowl. Hope you will enjoy the reading, although in Italian only. Merry Christmas and Happy New Year ! Gian
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