text: Fraunhofer also developed a diffraction grating in 1821, after James Gregory discovered the phenomenon of diffraction grating and after the American astronomer David Rittenhouse invented the first manmade diffraction grating in 1785. Fraunhofer was the first who used a diffraction grating to obtain line spectra and the first who measured the wavelengths of spectral lines with a diffraction grating.
  Ultimately, however, his primary passion was still practical optics; he once wrote that "In all my experiments I could, owing to lack of time, pay attention to only those matters which appeared to have a bearing upon practical optics".