Solar Observatory of Sacramento Peak.
The oscillations of the solar photosphere have been discovered due to the matter fluctuations and the displacements of the associated spectral lines (Doppler effect).
Two methods have been used :
- Noyes, Leighton and Simon (1962) made the subtraction of two spectroheliograms of the Sun as a whole, obtained in the blue and red wings of the same spectral line.
- Evans and Michard (1962) measured some displacements of spectral lines in spectra of a given region of the Sun.
The second method had the advantage of highlighting the vertical propagation of oscillations in the atmosphere of the Sun via the simultaneous observation of lines formed at different heights.
The first observations and measures of the displacements of the spectral lines in the spectrum of the Sun were made in the Sacramento Peak Observatory (Arizona).