To find some authority for the understanding that the Italian hours begin at the end of dusk, or about half an hour after sunset, I note that in the BBS Sundial Glossary under “hour plane” - “Italian” it says -
“there is some evidence in older works that Italian hours were counted from 30 minutes after sunset.” http://sundialsoc.org.uk/discussions/glossary-a-z/8/ Does anyone know what this evidence in older works is? A few other places I've looked - Wikipedia says “end of dusk, i.e. half an hour after sunset.” https://en.wikipedia.org/wiki/Hour This looked promising - Mario Arnaldi, Le ore italiane. Origine e declino di uno dei più importanti sistemi orari del passato (prima parte). https://www.academia.edu/2021250/Le_ore_italiane._Origine_e_declino_di_uno_dei_piu_importanti_sistemi_orari_del_passato_prima_parte_ But he does not mention the notion of "a half hour after" (mezz'ora dopo) sunset (tramonto del sole). Ross Caldwell 43.349399 3.22422981 Béziers, France ________________________________ De : sundial <sundial-boun...@uni-koeln.de> de la part de Ross Sinclair Caldwell <belmu...@hotmail.com> Envoyé : mercredi 1 juillet 2020 16:41 À : John Davis <john.davi...@btopenworld.com>; Schechner, Sara <sche...@fas.harvard.edu> Cc : 'sundial list sundials' <sundial@uni-koeln.de> Objet : RE: Time problem Hi John, Sara et al., My understanding is that a seasonal (or unequal) hour is a period of time ('in the first hour' etc) and not an instant. It is never divided up into minutes and so the time of 6 minutes after dawn must be referring to a time in equal hours, most probably measured with an astrolabe as you suggest. I agree. All that remains unknowable is the visibilty at the time. If it were overcast at dawn, they must have calculated rather than observed. But I tend to think it was observed, and determined with an astrolabe. Ross ________________________________ De : John Davis <john.davi...@btopenworld.com> Envoyé : mercredi 1 juillet 2020 10:10 À : Ross Sinclair Caldwell <belmu...@hotmail.com>; Schechner, Sara <sche...@fas.harvard.edu> Cc : 'sundial list sundials' <sundial@uni-koeln.de> Objet : RE: Time problem Hi Sara, Ross et al, My understanding is that a seasonal (or unequal) hour is a period of time ('in the first hour' etc) and not an instant. It is never divided up into minutes and so the time of 6 minutes after dawn must be referring to a time in equal hours, most probably measured with an astrolabe as you suggest. Regards, John ----------------------- ------ Original Message ------ From: "Schechner, Sara" <sche...@fas.harvard.edu> To: "Ross Sinclair Caldwell" <belmu...@hotmail.com> Cc: "'sundial list sundials'" <sundial@uni-koeln.de> Sent: Tuesday, 30 Jun, 20 At 21:20 Subject: RE: Time problem >>> In short, I am researching the biography of Filippo Maria Visconti >>> (1392-1447), duke of Milan, and you probably know that these Italian >>> princes relied heavily on astrology. So, Visconti's time of birth is known >>> precisely - "six minutes after sunrise," Monday, 23 September, 1392. His >>> natal chart was of course produced and interpreted, but it has been lost. I >>> am trying to recreate it as it might have been done by a court astrologer >>> of the time.<<< I have some thoughts about ascertaining the time of “6 minutes after sunrise” in 1392 in Milan. First of all, Milan is one of the earliest towns to have a public tower clock in the 14th century, but it would only strike and show hours according to local solar time. It would not be divided into minutes. It was not reliable enough for such a horological chart. Sundials would be the more commonly used timepiece, but the six-minutes is an unusual amount of precision. My guess is that the court astronomer was using an astrolabe, which can be divided into units in the range of 4-6 minutes. Many also had arcs for the astrological houses and for both equal and unequal hours. The actual time might have been taken from a bright star still visible in the dawn. It is also worth considering what this 6-minutes after dawn really means. Is the astrologer using unequal hours which were still more common in these early days of clocks? If so, then six minutes would be equal to 1/10 of the first hour on that day of the year—i.e., 1/10 of 1/12 of the length of daylight. Lastly, in reconstructing a horoscope, one needs to know the position of the planets to place them on the chart. Some might be observed, but mostly they are taken from a table. These varied in different manuscript traditions. Do we have a clue what table the astrologer was using? Good luck with your project. Sara Sara J. Schechner, Ph.D. David P. Wheatland Curator of the Collection of Historical Scientific Instruments Lecturer on the History of Science Department of the History of Science, Harvard University Science Center 251c, 1 Oxford Street, Cambridge, MA 02138 Tel: 617-496-9542 | Fax: 617-495-3344 sche...@fas.harvard.edu<mailto:sche...@fas.harvard.edu> | @SaraSchechner http://scholar.harvard.edu/saraschechner http://chsi.harvard.edu/ ________________________________ --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial Dr J Davis Flowton Dials http://www.flowton-dials.co.uk/ BSS Editor http://sundialsoc.org.uk/publications/the-bss-bulletin/<http://www.sundialsoc.org.uk/bulletin.php>
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