Working with photographic spectra
Cannon examined glass plates on which starlight was dispersed into spectra, comparing the appearance and strength of spectral lines. She also observed at telescopes, including photographing southern stars in Peru, rather than working exclusively on daytime calculations.
References: [2]
Classification and catalogues
Revising Williamina Fleming’s scheme, she rearranged and subdivided spectral classes into the O, B, A, F, G, K, M sequence. She published a spectral catalogue in 1901 and undertook extensive classification for the Henry Draper Catalogue and its extensions.
Photographs and appointment
Named Curator of Astronomical Photographs in 1911, she received a regular Harvard appointment as William C. Bond Astronomer in 1938. She retired in 1940 and died the following year. Her notebooks and photographic material survive as research records.
References: [1]