Use of a Lenard-window Image Tube for Astronomical Spectrophotometry

Abstract

This chapter focuses on the use of a mica-window electronographic image tube to replace the photographic plate in astronomical spectrophotometry at medium dispersion. The image tube is used in order to obtain improved noise-equivalent quantum efficiency that by varying the parameters of the stellar exposure, may be exploited in various ways: to secure higher photometric accuracy; to obtain spectra of more stars during rather brief spells of clear weather; or to obtain long-exposure spectra of fainter stars, when the freedom from reciprocity failure is also important. The image tube is being tested as a replacement for the photographic plate under operational conditions that may be unfavorable to the tube. Few users have reported on the application of image tubes to precise spectrophotometry. However, the radical alteration of the spectrographic system would not be justified until the usefulness of the image tube in routine spectrophotometry is established. The tube will be used in a program in which spectra are also being taken on photographic plates, so that a direct comparison of photometric results will be possible.