About The Project

Organizer

This project is organized by Honorable Lord Jon Chesey (mka Jon Voisey). He is based in the Barony of Three Rivers in the Kingdom of Calontir.

Mundanely, Jon has a BS in Astronomy and became interested in historical astronomy in 2017 when he began wondering how astronomers in the medieval period used mathematical models to calculate the positions of the stars and planets. Since information on this topic was nearly impossible to find, Jon turned to translations of the primary sources to determine how astronomers derived and used these models. In 2018, Jon began working through Ptolemy's Almagest. To attempt to make the material more accessible to those in the future, Jon has explained the Almagest as he progresses through it in his blog as well as teaching numerous classes on the subject.

To supplement his mathematical research, Jon has also recreated an astronomical quadrant which he uses to make observations of the stars and planets in an effort to create his own star catalog using period methodology. This instrument has been featured in Sky & Telescope magazine (June 2021).

Impetus for the Project

The idea for the project came as Jon reviewed Ptolemy's star catalog. While reading on the history and development of critical editions, Jon found the following quote from translator G. J. Toomer:

Ideally one should provide a reconstruction of the outline of each constellation as it appears on Ptolemy's star-globe. Unfortunately no one has done the necessary work of assembling and comparing all the literary and iconographic evidence from antiquity and from the derivative Arabic tradition (notably as-Sufi). This would be an interesting and valuable enterprise.

- G. J. Toomer

In other words, historians of astronomy have a poor understanding of how the constellations were envisioned in antiquity as no thorough investigation of their depictions has been conducted.

While this project does not fully address that need, it is a first effort in attempting to capture how Ptolemy might have imagined them based on this single source. Interested individuals are encouraged to explore beyond the provided material and uncover how these depictions may have changed over the ages.

Furthermore, the history of astronomy is an under-researched topic within the SCA. This project is intended to be a gateway for those interested to study the topic.

An image of Ursa major from John Bayer's Uranometria (1603).