A steerable 0.25‐m Ebert monochromator and photomultiplier detector were employed to measure the spectra of the clear daytime sky (Rayleigh scattering). The day sky intensity as a function of wavelength was observed to vary as λ−4in agreement with Rayleigh’s predictions and observations. The same monochromator and detector with the addition of a multichannel scaler were used to observe the night sky spectra (airglow). The oxygen (OI) emission at 557.7 nm was observed from the ground by using this technique.