Measuring solar altitude using medieval instruments

Historical astronomical instruments, such as the quadrant and the triquetrum, were integral to the development of observational astronomy from the time of Ptolemy through the Islamic Golden Age and the European Renaissance. This study investigates the practical accuracy and educational utility of these tools by designing and constructing functional replicas using CNC engraving techniques.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To evaluate their performance, solar altitude measurements were recorded over a five-hour period and compared with precise data from the Stellarium software. While the quadrant demonstrated high alignment with Stellarium’s computational models, the triquetrum exhibited a zero offset of approximately +6° due to structural flexing of its wooden stand.

Potential design refinements using rigid materials are discussed, and it is concluded that these instruments can serve as effective pedagogical tools for introducing students to the history of science and the fundamentals of celestial observation, especially in medieval times.

 

 

 

 

 

 

 

 

 

 

After some adjustments and improvements to the hardware, fresh data was acquired on 13th of February, 2026, which is shown here.