There were several difficulties with this interpretation that he pointed out. Not the least of which is that if it were Doppler, then not only should each photon be stretched out by the Doppler effect, but also the distance between each photon. Because the photon flux is reduced, this causes the object undergoing a Doppler redshift to appear less bright than a corresponding object undergoing a non-doppler redshift. Hubble knew his observations were not in agreement with this brightness correction. As big bang theorists attempt to solve the age problem by making the time to the big bang longer, they exacerbate the quasar problem.
Quasars become even farther away and intrinsically brighter.
Yet their temperature remains that of ordinary stars as exhibited by emission spectra of metallic ions that can only exist at a limited range of temperature. They are known to be about stellar size since they vary in brightness on a scale of a few minutes to seconds. They must have an intrinsic non-Doppler redshift and be nearby to be explained. If neutrinos have mass about 1 ten millionth the mass of the electron, their Compton Effect red shift would be 10 million times that of that of the electron. The probability of a neutrino Compton Effect remains to be determined.