In 1814 he made the first spectrometer, to measure the dispersive power of lenses, using a yellow flame as the light source. He compared the flame spectrum with a spectrum of the Sun produced by a prism, noting and recording the positions of the Sun’s Fraunhofer lines. He later noted similar lines in the spectra of other stars. Fraunhofer also made achromatic lenses and the first diffraction grating, developed the equatorial mount, and constructed the 16-cm heliometer used by F. W. Bessel to measure the parallax of 61 Cygni.