Precarious innovation in Francoist Spain: biography of an orbigraph

By Anxo Vidal Nogueira, University of Valencia, Spain

This research was supported by a SIS Grant. A longer piece on this subject will feature in a future SIS Bulletin.

Figure 1: The orbigraph with the original table on which it was used, as well as the paperweights and an original calculation sheet. A and B are as described in the text. Table length in the vertical axis: 125 cm. Source: image taken by the author.

Object biographies are a well-established approach in studies of the material culture of science (Pantalony, 2011; Anderson, 2013; Lourenço and Gessner, 2014). They offer the opportunity to deepen our understanding of the complex and often unknown relationship between scientific practice, community and technology. In this post I will explain the first results of my ongoing project, which reconstructs the biography of an orbigraph, a mathematical instrument located in the astronomical observatory of the Universidade de Santiago de Compostela (Galicia, Spain).

The orbigraph is a special kind of integraph (a mechanical analogue computing device for plotting the integral of a graphically defined function) which allows the determination of the orbit of a double start. Its configuration consists of two main arms in a cross arrangement, working one of them as a rail in which the other can slide (see Figure 1). The rest of the apparatus is a group of arms assembled in such a way that when the point A describes a curve, the B point responds with another curve related to the first one by this mathematical expression:

𝜌2𝜃˙ = constant

This is basically Kepler’s square law, when the curves are the time evolution of the relative distance ρ and angle θ of two astronomical bodies. In short, sketching one of the curves, the orbigraph draws the other fulfilling Kepler’s law.

Figure 2. Press coverage of the observatory activities, with Vidal Abascal and the orbigraph as its protagonists. Published in Diario La Noche, February 10, 1959. Source: Galiciana, Biblioteca Dixital de Galicia (

The orbigraph was designed by the Galician mathematician and astronomer Enrique Vidal Abascal (1908-1994) circa 1950. It is still unclear when did he start working on it. We know for sure that by the year 1952 the observatory started the administrative process to receive an extraordinary economic assignment for its construction. This search for budget support and the apparatus construction itself took a long time, starting in 1952 and finishing only in February 1955, when the actual object arrived at the observatory. The making of the instrument was offered to at least three different companies, two Spanish and one outside Spain. Both Spanish companies declined the offer, arguing a work overload or a lack of experience in the field. Finally, the Swiss company Coradi accepted the project for 17,000 Swiss francs.

The orbigraph became arguably the most important technology at the Santiago observatory, perhaps even more than the telescopes themselves. This is not a surprise considering that the double-star study was the main task of the observatory and the orbigraph facilitated it in a very considerable manner. It was perfectly inscribed in the observatory’s scientific production, systematically used for around 25 years, although it is difficult to establish the last time it was used. In the observatory infrastructure, it was a fundamental element as shown in the plan of the 1961 observatory expansion project, in which it had its own dedicated office.

The orbigraph, moreover, appears to have been a tool of social and scientific status for the observatory and for its designer, considering its presence in contemporary newspaper coverage. In a precarious context with limited scientific production and achievements, the orbigraph original design and, specially, its international construction could be considered a milestone. Vidal Abascal’s identification as the orbigraph creator lasted throughout his life, not only in the public arena but also within the academic community, being systematically mentioned in all the obituaries made after his death.

The orbigraph’s life is immersed in a very complex background in which many elements played a role. I hope to investigate this case with more documented sources, which I have already located, in a second research trip to Galicia.


Pantalony, D. 2011: Biography of an Artifact: The Theratron Junior and Canada’s Atomic Age. Scientia Canadensis, 34(1), 51-63

Anderson, K. 2013: Beyond the Glass Cabinet: The History of Scientific Instruments. Revista Electrónica de Fuentes y Archivos, 4(4), 34-46

Lourenço, M. C. and Gessner, S. 2014: Documenting Collections: Cornerstones for more history of science in museums. Science & Education, 23(4), 727-745

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