John of Saxony (astronomer)
John of Saxony (also Johannes de Saxonia, John Danko or Dancowe of Saxony) was a medieval astronomer. Although his exact birthplace is unknown it is believed he was born in Germany, most likely Magdeburg. His scholarly work is believed to date from the end of the 13th century into the mid 14th century. He spent most of his active career, from about 1327 to 1355, at the University of Paris.[1]
Scholarship
John of Saxony is quoted in various medieval manuscripts and referenced as the author of various astronomical or astrological treatises, even though his authorship in some cases is questionable.
A computus dating back to 1297 is attributed to John of Saxony even though the author is listed as Iohannes Alemanus. The fact that the geographical longitudes of Paris and Magdeburg, considered John's birthplace, among other facts is why some historians consider him the author.
Viewed with less suspicion is his commentary on Liber Introductorius ad Magisterium Idiciorum Astrorum written by al-Qabisi (
Among his other contributions were a commentary on
John of Saxony was of the opinion that astronomers of that time wrote their works in such a confusing manner that those who weren't trained in the field couldn't comprehend nor use them appropriately. Under the tutelage of his master,
Alfonsine Tables
The more widely recognized work by John of Saxony is his Canons on the
In order to study the tables, they were translated from Castillian into Latin, which was the scholarly language of the day. This is due in large part to the Catholic upbringing of the day in medieval Europe. This act alone allowed greater access and understanding of astronomical work to that point. In 1327 he added an influential set of explanations and instructions (Canons) to the revision of the
The canons of John of Saxony explained how one could find the planetary position (longitudes) at any given time. One would have to calculate the length of time between the basic year and the year sought. They would then divide them by mean figures of the planetary orbits, and add/subtract values to adjust for hours and minutes. To expedite these calculations he had an accompanying table of sexagesimal multiplication.[7] In addition to this, he divided the day into sixty parts rather than 24 hours, consistently representing time by sexagesimal fractions and multiples of a day. It is in this form that the Alfonsine tables circulated in Western Europe for the next three centuries.[8]
After translation and Canons were added to the Alfonsine Tables, they were disseminated from Paris to the rest of medieval Europe. As they were received, the tables were converted to the local meridians for proper use. Although widely used, a published print version of the tables and John of Saxony's Canons didn't exist. It wasn't until 1483 when
References
- ^ ISBN 140394766X.
- ^ Introductorium ad judicia astronomiae, Herbermann, Charles, ed. (1913). Catholic Encyclopedia. New York: Robert Appleton Company. .
- ^ Lynn Thorndike, A History of Magic and Experimental Science, vol. 3, (New York: Columbia University Press, 1934), pp. 262-6.
- ISBN 0231087977.
- ISBN 0801880556.
- ISBN 978-0387351339.
- ^ Kusukawa, Sachiko. "Astronomical Tables". Starry Messenger. University of Cambridge. Retrieved 3 June 2014.
- ^ Lynn Thorndike, A History of Magic and Experimental Science, vol. 3, (New York: Columbia University Press, 1934), pp. 253-8, 267.