SIMBAD references

We have digitized 24 spectrograms from the 1928 to 1930 eclipse of ϵ Aurigae, a binary system that has generated extensive investigation due to its long 27.1 yr period and enigmatic secondary, which is completely obscured. The spectrograms that we have digitized comprise the earliest campaign undertaken by the Yerkes Observatory astronomers to record an eclipse of ϵ Aurigae. In this article, we describe our methods of digitization and compare our data with more contemporary spectrogram digitizations. This work demonstrates the quality of scientific data extracted from historical analog material to expand the range of time-domain astronomy. The calibrated spectra are made available via OCHRE, a comprehensive research database, for public use.