Spectrophotometric accuracy of spectra obtained from spectroscopic plates measured with a commercial flatbed scanner

The intensity spectra recovered from the spectroscopic photographic plates were compared with the CCD spectra, and we found the difference between the two was only a few percent. The measurements were taken using a commercial flatbed scanner instead of a microdensitometer. The results indicate that the following two statements are inaccurate: (1) Correct measurement of spectroscopic plates requires a microdensitometer and a commercial flatbed scanner is insufficient; (2) The accuracy of the spectrum obtained from spectroscopic plates is approximately 10%. These results will encourage the creation and publication of a digital archive of spectroscopic plates. This paper presents the evaluated results of the optical resolution of the flatbed scanner, the measurement of spectroscopic plates, the method of recovering intensity spectra from photographic density data, and the results of comparison with CCD spectra, and discusses the causes of the high accuracy spectra obtained with the flatbed scanner.