Application of dicyanin to the photography of stellar spectra
A 1919 technical paper issued by the National Bureau of Standards in Washington on using dicyanin-sensitized plates to photograph stellar spectra, written for physicists and observatory astronomers. The plates are halftone reproductions of spectrograms: short white and grey bands floating in dense black rectangles, edged with ruled tick marks and small wavelength labels such as H,K, 486, 706 and 760, useful for high-contrast black fields, measured-scale annotation and abstract bands of light.
