Performance of Image Tubes in the Coudé Spectrograph at Mount Stromlo Observatory

Abstract

Publisher Summary Several five-stage secondary-emission image intensifying tubes made by 20th Century Electronics Ltd., have been tested in the laboratory and in the coude spectrograph of the Mount Stromlo Observatory. Comparisons have been made between the rate at which information is accumulated by transmission secondary-emission image intensifying tubes and by IIa-0 emulsion. These comparisons were done at Imperial College on the basis of projected test images, and have been continued at the Mount Stromlo Observatory, A.C.T., Australia, where the coude spectrograph was used for direct comparisons of performance on the spectra of stars and of the sky. The spectrum of the sky that is almost identical with the spectrum of the Sun has been used extensively at Mount Stromlo for testing the performance of image tubes. Moreover, experimental studies based on the sky spectrum do not interfere with the use of the telescope for stellar programs at night. At Mount Stromlo, an etalon has been mounted in the parallel beam between the collimator and the grating in the coude spectrograph. The spectrograph at Mount Stromlo is mounted in a fixed position, in an excavation at the lower end of the polar axis of the 74-in. telescope. It is enclosed in a 9-in. thick concrete housing, surrounded by 4 - in. of expanded plastic insulation.