08 A realistic delineation of a solar prominence via a spectroscope

This engraving, following an early solar spectrogram, shows realistically how a typical loop prominence can be seen through a solar spectroscope, or recorded in a spectrograph, outside of a total solar eclipse. Key points in the technique include 1) only light from the solar chromosphere enters the slit; 2) the slit is opened wide; 3) the spectrograph is tuned to a naturally wide absorption line, in this case hydrogen alpha. Concepts demonstrated here are helpful in understanding Hale's revolutionary photographic technique with the spectroheliograph. Illustration originally published in "The Sun" by Charles A. Young.