International congress of byzantine studies belgrade, 22 27 august 2016

Alberto Bardi
Ludwig-Maximilians-Universität, Munich, Germany; 
[e-mail]
Bessarion and Persian Astronomy
In 13
th
and 14
th
century Byzantium foreign astronomical knowledge, especially the one 
stemming to Persian tradition, gets the attention of Byzantine scholars. Among the byzantine 
scholars interested in astronomy is Cardinal Bessarion.
Bessarion’s interest in astronomy, especially for Ptolemy’s Almagest, as well as his relationship 
with the astronomer Regiomontanus and his controversy with Georgios Trapezountios are well 
known. Nevertheless this interest of Bessarion lacks of detailed analysis from technical point of 
view: his collections of astronomical and mathematical text have never been carefully surveyed.
However Bessarion is among the scholars writing Greek texts of Persian astronomical 
tradition. In fact he is the copyist of an anonymous astronomical text of Persian tradition contained 
in the manuscript Marcianus graecus 333 Z (dated before 1450). This text is entitled Παράδοσις 
εἰς τοὺς περσικοὺς κανόνας (Instructions for the Persian Handy Tables), it is delivered in almost 
eighteen manuscripts, among which the oldest was written before the year 1374 by the byzantine 
mathematician Isaak Argyros (ca. 1300-1375); it is still unpublished, I am currently working at its 
edition. The Text is a commentary to Persian astronomical handy tables, a widely-spread genre from 

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139
13
th
century on in Byzantium. The genre’s ancient model is the Small Commentary to the Handy 
Tables by Theon of Alexandria (4th century), while the most recent model is the Commentary by 
Stephanus Alexandrinus (7
th
century).
The manuscript Marc.gr.333 Z contains also other astronomical and mathematical texts (e.g. 
Euclid), all written by the hand of Bessarion.
My paper focuses on Bessarion’s mathematical integrations I found out in the Persian 
astronomical text copied by himself in the manuscript Marcianus graecus 333 Z. I give some 
information about the text from both historical-philological and astronomical perspective, then I 
consider and explain the importance of Bessarion’s mathematical integrations.
Compared to the texts delivered in the manuscripts of the Instructions, the text written by 
Bessarion contains two essential differences: a text-addition and algorithms. The text addition is a 
calculation method for syzygies (conjunction of sun and moon), which is not attested in the other 
manuscripts. In most passages where the other manuscripts deliver calculation tables, Bessarion 
writes the same calculation, but in algorithmic form.
The additional text and also the algorithms were brought into the Instructions by Bessarion 
during the writing process: I found out that he integrated this text from an astronomical work 
contained in the manuscript Vaticanus graecus 1059 (beginning 15
th
century), written by 
John Chortasmenos, master of Bessarion in Constantinople: here the additional text is among 
astronomical texts of Isaac Argyros and the algorithms are in the Third Book of the astronomical 
work by Theodoros Meliteniotes. Among the algorithms only one is original by Bessarion and it 
deals with the latitude of Mercury and Venus.
The legitimization of this mathematical procedures has its roots in the ancient mathematical 
works, e. g. the Metrica von Heron (1
st
century A. D.), the works of Diophantus, Pappus and Theon 
from Alexandria: this is a canonical language survived for thousand years.
Bessarion’s integrations provide evidence of his activity during his learning years (before 1440) 
at the school of Chortasmenos and Plethon as well as his abilities in using the mathematical language.