Spectroheliograph

The Spektroheliograf is an instrument for solar research (Greek Helios = sun ), in particular the chromosphere. He's a big -grating monochromator and used for photographic recording of solar images ( Spektroheliogramm ) in a very narrow wavelength range (< 0.01 nm) of the light. Most frequently the spectral line K of calcium II used therefor.

The lens of a large telescope forms an image of the sun, of which the slit of the monochromator lets through only a thin strip. This is spectrally dispersed and hidden by a narrow range of wavelengths.

Behind it is a photographic plate, in which the monochromator is moved slowly. This one gets a scan ( a scan ) of the entire solar disk in the selected spectral range.

The principle can be converted to modern CCD sensors.

The invention of the Spektroheliografen goes back to work in parallel by George Ellery Hale in the U.S. and Henri -Alexandre Deslandres at the Observatory of Meudon, near Paris. 1932, the system was expanded by Robert R. McMath to the possibility of filming.