Dear friends, a new issue of the Italian magazine Orologi Solari is available for download from the usual site http://www.orologisolari.eu/. It's a special issue dedicated to our gnomonist friend Alessandro Gunella.
Here is the list of articles together with a short abstract: 1. "Curriculum vitae (self-produced)" by Gunella Alessandro 2."Note on the book by Giuseppe Sacchi <Gnomonica piana> - Pavia 1846" by Gunella Alessandro In this article the author takes the opportunity from the recommendation of the book by Giuseppe Sacchi to discuss the problem of the "three points". This problem has been faced over the centuries by many experts in the sector, starting from Vitruvius to Zarbula and passing through Igino Gromatico, Al Biruni, Nuñes, Clavio, Kircher, Grienberger, Oddi, Ozanam, Desargues, Guarini, De la Hire, Mahistre. 3. "Stefano Di Giovanni: an author from the 19th century who plays with the Italic Hours" by Gunella Alessandro The study of Italian sundials in the nineteenth century benefited from a considerable theoretical research, although as a matter of fact (or maybe because) this kind of dials was no longer in use. In 1843, Father Stefano Di Giovanni publishes a theoretical study with which he identifies new criteria for tracing Italic sundials on horizontal planes. He also proposes the use of a particular hour line, which he calls "Verticale Italico", for the correct regulation of mechanical clocks and he finally identifies a particular mathematical curve which he calls "Orizzontoide". 4. "A small techique by Clavio not to <get out of the sheet>" by Gunella Alessandro The article is inspired by a 24-page booklet "Compendium brevissimum describendorum Horologiorum ..." written by Clavius in 1603. When you build a non-declining (or horizontal) sundial with the classic graphical method, sometimes the more distant lines from noon (like the lines of the hours 8 and 7 o'clock in the morning, or the correspondents in the afternoon) have very distant references on the Equinoxial line. Clavius in his handbook indicates a method to remedy this problem. The author of this article explains the geometric reasons why this method works. 5. "The declination of the Sun in a day of <n> hours" by Gunella Alessandro It is here proposed to look for the declination of the parallel covered by the Sun on a day when the hours of light are "n", and the night is 24-n hours, in a place where Latitude is given, by means of a graphical method. The solution is based on the sixteenth-century text by G. B. Benedetti. 6. "Notes about Italic sundials" by Gunella Alessandro The article is a summary, very partial of topics concerning the Italic hours, debated here and there in texts from the 16th and 17th centuries. 7- "The extreme points of the Italic hours" by Gunella Alessandro The author, inspired by the "usual" book "De gnomonum umbrarumque ..." published in 1573 by G. B. Benedetti, explains in this article how to find the extreme points of the Italic lines without using the solstice curves built for equal hours sundials. 8. "Apianus and the graphical solution for spherical triangles" by Gunella Alessandro The solution of spherical triangles is here debated with a graphical method starting from what Apianus explained in 1540 in his book "Astronomicum Caesareum", using a universal astrolabe called " Arzaquiel's Scaphea" 9. "A bifilar sundials with two catenaries solved graphically" by Gunella Alessandro In this article the author "challenges" vector algebra. A graphical solution is presented for the construction of a bifilar sundial with wires arranged as catenaries. 10. "The Gnomonic Transformation" by Gunella Alessandro In this article the author is inspired by a Gnudi's text from 1700 entitled "La Tramutazione Gnomonica" or the method to build any vertical declining sundial starting from a horizontal sundial. The method here described is a reworked version by the author. 11. "Exactly the same: a predecessor of the Vinaccia diagram" by Gunella Alessandro The Vinaccia diagram was discussed by Gunella in n. 13 of this magazine. "The Analemma and the Universal Compass" was the title of the article. But already in the work by Father Egidi "Un Orologio Solare Universale" published in Rome in 1881 and so preceding Vinaccia publication, a method is shown to find local time for any latitude: a first step towards Vinaccia diagram. This method is here briefly illustrated. 12. "A horizontal Italic sundial by Foster – Lambert" by Gunella Alessandro In issue 24 number 2 of the NASS magazine "The Compendium" an interesting sundial proposed by Steve Lelievre, a Canadian gnomonist from Vancouver, showed off on the cover. This is an interactive horizontal Italic sundial of the Foster Lambert type. In this article an analysis of the author, using the usual graphical method, is exposed. A digital bonus can also be downloaded for additional reference material. Hope you will enjoy the reading, although in Italian only. Ciao. Gian Casalegno
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