Rubuta ci gaba ga wannan sakin layi - Bayan ritayar Pickering a 1921, Daraktan HCO ya koma Harlow Shapley (babban mahalarta a cikin abin da ake kira "Babban Muhawarar
" na 1920). Wannan zamanin na Observatory ya zama sananne ne ta hanyar aikin Cecelia Payne-Gaposchkin, wanda ya zama mace ta farko da ta sami digiri na PhD a fannin ilmin taurari daga Kwalejin Radcliffe (a takaice daga Observatory). Bayanin Payne-Gapochkin na 1925 ya ba da shawarar cewa taurari sun ƙunshi hydrogen da helium, ra'ayin da aka yi wa ba'a a lokacin. Tsakanin aikin Shapley da kuma kafa CfA, Donald H. Menzel ne ya jagoranci gidan kallo sannan kuma Leo Goldberg, dukansu biyu sun ci gaba da shirye-shiryen da aka sani a cikin hasken rana da tauraron tauraron dan adam. Menzel ya taka muhimmiyar rawa wajen ƙarfafa Smithsonian Astrophysical Observatory don matsawa zuwa Cambridge kuma ya yi aiki tare da HCO.