Beyond models and parameters: astronomer computational practices. Toward a shared Python Library for DISHAS

Org. Matthieu Husson

Dates: 11-13 Nov. 2020, 14h-16h

Place: virtual session/Paris Observatory



Recent research in astronomical table analysis shows a growing awareness of the importance of historical actors’ computational practices.  While it remains crucial to think carefully about the models and their parameters, it appears also more and more clearly that these are distant from the historical actors and will not allow a fine grained understanding of how they actually generated and used the tables attested in the sources. For these later aims, a close consideration of different aspects seems decisive. These aspects comprise:

  • the way to perform basic arithmetical operations (often depending deeply on numerical notation systems and including “rounding”)
  • the way to execute interpolation when “reading”  tables
  • the importance of identifying the exact tables used (with their potential idiosyncratic manuscript variants),
  • the way to organise large computation “by hand” according to specific procedures.

Beyond tables themselves, different sources (including canons, arithmetical texts or computed examples) provide clues about these computational practices and were recently analysed in this respect. Other research has explored the different types of noise produced by table variants in manuscripts, changes in interpolations algorithms, or in higher level procedures. Direct research on specific tables are also able, in some situations, to provide results on such fine grained aspects of the procedures which generated the tabulated values.

These research often rely on the use of different kinds of computer programming where portions of historical actors’ computational practices are emulated and explored more or less systematically or empirically. The collective enterprise of DISHAS offers us an opportunity of scaling up these local and converging initiatives into a shared and collaborative tool interfaced with the other tools of DISHAS (e.g. DTI,CATE, DIPS, etc.). The goal of this workshop is to shape the main contour of this collaborative tool and to define collectively what can be the first steps to take in the following year to build an initial functional and useful device (for instance generating ephemerides?).

This collective effort will  be rewarding by opening up new ways to share our work and mutually benefit from each other’s results (if only by changing the way we can publish on table cracking). In the midterm it will also certainly allow us to explore in a more systematic manner fundamental questions about this kind of research like: How precise can we hope to be in reconstructing the computation scenario that generated a given historical table given the information provided by the table values and its historical context? It also opens new areas for research in connection with recent advances in data-analysis, optimisation and Machine Learning.

In practical terms, this workshop will take the form of three two hours virtual sessions. These three sessions will consist of five talks show-casing the recent research trends around astronomers computational practices briefly sketched above and one final collective discussion. This workshop will associate in the conversation history of astronomy scholars and digital humaniteis and data analysis so we can work in realistic directions in terms of actual practices  and opportunities offered by the convergence of these fields.


Wednesday 11, 2020


Benno van Dalen

Some practical examples of Islamic computational techniques: Abu ‘l-Wafa al-Buzjani and Kushyar ibn Labban


Matthieu Husson

Exploring computation practices with tables in the Alfonsine traditions: clues in arithmetical texts, canons and computed examples



Thursday 12, 2020


Camille Bui

Computing Latitude tables in the 14th century: from canons to Python


Stefan Zieme

Implementing historical calculational schemes: Oblique ascension in the Almagest


Friday 13, 2020


Richard L. Kremer

Ephemerides from TABLES to spreadsheets to DISHAS, or what do we want from modern tabular computation … and why


General discussion