Detection and measurement of total ozone from stellar spectra: Paper 2. Historic data from 1935–1942

Abstract. Atmospheric ozone columns are derived from historic stellar spectra observed between 1935 and 1942 at Mount Wilson Observatory, California. Comparisons with contemporary measurements in the Arosa database show a generally close correspondence, while a similar comparison with more sparse data from Table Mountain reveals a difference of ~15–20%, as has also been found by other researches of the latter data. The results of the analysis indicate that astronomy's archives command considerable potential for investigating the natural levels of ozone and its variability during the decades prior to anthropogenic interference.