Spectrophotometric Techniques

Abstract

Photographic spectrophotometry is a basic method of studying stellar spectra that is of continuing value. This method is most valuable for making measurements of the relative intensity distribution in the stellar spectrum over short wave-length intervals. The determination of absolute intensities by photographic techniques is a very difficult problem, for one must take account of the varying transmission and sensitivity of the instruments and of the sky. These factors will vary with time and with the wave length at which the observations are made. Absolute measurements of the light intensity in stellar spectra are rarely attempted. Furthermore, the theory of stellar spectra is used to predict relative intensities within a line profile for comparison with observed intensities, rather than absolute values, and all present methods of analysis are aimed at obtaining information from relative intensities.