A spectroheliograph is an astronomical instrument making it possible to obtain monochromatic images Sun, i.e. in a given Wavelength (relative to a chemical element such as the Hydrogène, the Calcium, etc).

History

It is in August 1868 that Jules Jansen observed successfully the protuberances apart from an eclipse by using a spectroscope centered on the line Hα whose broad slit was pointed on solar limb.

Following this success, in the years 1880-1890, Georges E. Hauls and Henri Deslandre will develop independently the spectrohélioscope (visual) and the spectroheliograph (photographic).

Optical principle

Its optical principle is the following:

When the slit of entry of the spectroscope sweeps the image of the Sun slowly given by the objective of its glasses, a complete image of the protuberances is formed on the photographic plate which one makes ravel at the suitable speed behind the second slit of the spectroscope.

Examples of images