Surveying
Grating Spectrometer by Fraunhofer, Reichenbach, and Ertel, Inv. No. 2070. Photo: Deutsches Museum
In this spectral apparatus, light was dispersed into its color components not with a prism, but with a so-called diffraction grating. The spectral apparatus demonstrates how scientific instruments were developed at the Optical Institute.
The entire construction essentially corresponds to a theodolite — an instrument for land surveying that was sold in large numbers by the Optical Institute. The table for the diffraction grating was placed where the observation telescope would normally be, and the grating itself was observed through a telescope. Instead of measuring angles between two points in the landscape as in land surveying, the goal now was to determine the angles of deflection of the individual colors as accurately as possible. As a reference, Fraunhofer used the dark lines he discovered in the solar spectrum. Instead of being used for surveying land, the instrument was deployed to survey light.
This approach exemplifies the central importance of instrument-making to Fraunhofer’s scientific achievements. The ever more precise investigation and further development of scientific instruments dictated the direction of the work. Discoveries such as the dark lines in the spectrum initially emerged as a byproduct, but they led to further developments and research.
