XVIII. On the photographic spectra of stars

Abstract

§ I. Introduction . In the year 1876 I presented to the Royal Society a preliminary note on the “Photographic Spectra of Stars.” I beg now to give an account in greater detail of my methods of work and of the photographs which I have obtained. The importance of supplementing the observations by the eye of the spectra of stars by photographs of the violet and ultra-violet portions of their spectra was so obvious, that as early as the year 1863 my friend Dr. W. Allen Miller and I made the attempt to obtain such photographs in addition to our eye-measures of star spectra. With the apparatus then at our command we were not able to get any clear definition of lines, but a dark streak only upon the negative plate. Other investigations which I then took up prevented me from resuming this line of work. I was also not encouraged to proceed further with photography at that time, as the clock-motion driving the telescope did not work with the accuracy that was necessary.