The Sun’s chromosphere is a faint layer of gas surrounding the photosphere, its visible surface. The chromosphere glows crimson at a wavelength of 656.28 nanometers (nm). Astronomers call this wavelength the Hydrogen-alpha (Hα) line, and it lies in the red part of the spectrum.
Seeing the Sun in a new light
A Hydrogen-alpha filter will give you a new perspective on our daytime star.