Spectroheliograph
The spectroheliograph is an instrument for solar research ( Greek Helios = sun), especially the chromosphere . It is a large lattice - monochromator and is used for photographic recording of solar images ( Spektroheliogramm ) in a very narrow range of wavelengths of light (<0.01 nm). The red spectral line K of calcium II is most frequently used for this .
The objective of a large telescope produces an image of the sun , of which the slit of the monochromator only allows a thin strip to pass through. This is spectrally broken down and a narrow wavelength range is masked out of the spectrum through an exit slit. Behind this is a photo plate or an area detector, in front of which the monochromator is slowly moved. This results in a scan of the entire solar disk in the selected spectral range.
The principle can be applied to modern CCD - sensors convert.
The invention of the spectroheliograph goes back to parallel work by Henri-Alexandre Deslandres at the Paris Observatory Meudon (around 1892) and George Ellery Hale in the USA . In 1932, the system was expanded to include film recordings by Robert R. McMath .