Tag: Nicephorus Gregoras

Nicephorus Gregoras’s “περὶ κατασκευῆς … ἀστρολάβου”

An illustration of a rete from a 15th-century copy of Nicephorus Gregoras’s “περὶ κατασκευῆς καὶ γενέσεως ἀστρολάβου,” BN suppl. graec. 0652, fol. 285v.

A nice drawing of the rete from Nicephorus Gregoras’s “περὶ κατασκευῆς καὶ γενέσεως ἀστρολάβου” (“On the Mathematical Origin and Construction of the Astrolabe”). This rete, like other diagrams in copies of Gregoras’s text, lacks stars and finer details. In the few copies I’ve seen that include the stars, the rete closely resembles the one surviving Byzantine astrolabe, especially the number and style of the star pointers.

The only Byzantine astrolabe known to survive dates from the 11th century and reflects the style of other early, Islamic astrolabes. Today this astrolabes is in Brescia.

Interesting, at least to me, is the fact that the illustrations in different copies of Gregoras’s text often label the diagrams in different ways. In this copy diagrams are labeled counterclockwise starting at the 9 o’clock position, e.g., the diagrams on fol. 284v of BN suppl. graec. 0652. In other copies, diagrams are labeled counterclockwise or clockwise from various starting points (the 9 o’clock position is the most common starting point). In one manuscript, diagrams on consecutive folia are labeled in opposite ways. The absence of illustration in many copies of Gregoras’s work makes it challenging to follow the text. In most such cases, the copyist left no room for illustrations, suggesting he was working from an unillustrated copy. In some manuscripts, the copyist left large spaces for the illustrations.

Another Byzantine Wind Diagram

A 16th-century copy of a Byzantine wind diagram from BN Grec 2493, fol. 165v.

This Byzantine wind diagram, also titled “Diagram about thunder, storms, rainstorms, and earthquakes,” closely resembles the previous Byzantine Wind Diagram. Both come from latter 16th-century manuscripts. This particular copy was never finished—the elements are missing from the center of the diagram, the “παναχῆ” is also missing in this copy.[1] Once again, we see the aspects in the inner circle, the second square is meteorological phenomena, the 12 winds, the signs of the zodiac, south and north poles, and the captions indicating from the right and left parts of the cosmos.

As with the other codex, Royal MS 16 C XII, this codex (BN Grec 2493) contains three texts on the astrolabe—the catalog entry identifies them as Philoponus’s, an anonymous text,[2] and Gregoras’s along with scholia on that last work—and a variety of anonymous astronomical diagrams. The codex also includes texts by Theon of Alexandria.


  1. The image is b&w, so I can’t tell what color inks are used, but the division of inks between the different words also resembles that used in the other diagram. That is, the title, the caption along the perimeter, the poles, the signs of the zodiac, and the four aspects appear to be in a different (red?) ink.  ↩

  2. I suspect this is the text typically attributed to Ammonius, but I haven’t had the time to confirm that suspicion.  ↩

Images of Byzantium: Nicephorus Gregoras’s “On the Construction and Origin of the Astrolabe”

In 1498 Giorgio Valla published a Latin excerpt from Nicephorus Gregoras’s treatise “On the Construction and Origin of the Astrolabe.” Despite appearing as the fifth tract in Valla’s compendium, which included other Byzantine and Greek authors, Gregoras’s text quickly became a standard authority amongst scholars in 16th-century Europe. Authors such as Johannes Schöner and Peter Apian regularly cited him at various places in their own manuals on constructing and using astrolabes but do not appear to have read Gregoras’s text. Indeed, their familiarity with the Byzantine scholar seems to have been mediated through Valla’s excerpt.

This project has two parts. First, I am working on a critical edition and translation of Gregoras’s text. This volume will include a scholarly introduction that locates Gregoras and his work within the Byzantine tradition. The second part of the project explores how and why Gregoras became an authority for 16th-century Latin authors. This promises to illuminate how Byzantium came to occupy a place of intellectual and cultural importance in the sixteenth century, particularly amongst German scholars and humanists.

Nikephoros Gregoras and Byzantine Science

In March I am talking on the Byzantine polymath Nikephoros Gregoras and his efforts to establish his scientific authority. In “Empiricism, Prediction, and Instruments: The Creation of Expertise in 14th-Century Constantinople” I will examine the ways that Gregoras tried to distinguish his own expertise by grounding it in precise, empirical predictions and his command of technical knowledge.

This talk forms part of my larger project on Byzantine scientific knowledge. This larger project began from Gregoras’s text “On the Construction and Origin of the Astrolabe” (“Περὶ κατασκευαζῆς καὶ γενἐσεως ἀστρολάβου”).

A digram from Gregoras’s text on how to construct an astrolabe.