An apparatus is described that determines automatically the significant information of spectral plates. First the plate transmission is measured step by step along the spectrum, digitized, and stored on paper tape. This is processed by means of a computer programmed to find line positions and intensities and to calculate wavelengths and wavenumbers. The final wavelength precision as tested by means of thorium standard lines is of the order of a few 0.001 Å for a reciprocal dispersion of 0.9 Å/mm.
R. Hoekstra, "A Rapid Precision Wavelength Measuring Apparatus," Appl. Opt. 6, 807-811 (1967)