A method for the compensation of a variable light source in photoelectric spectrophotometry is presented. The outputs of a scanning photo-cell and a monitoring cell are fed to two amplifiers. The outputs of these amplifiers are then fed to a self-balancing recording potentiometer. The equipment has laboratory as well as astrophysical applications. The limiting magnitude at which useful spectrophotometry with a resolution of 1A is approximately 4. Further development work is in progress.
W. A. HILTNER and A. D. CODE, "The Compensation for Seeing in Stellar Photoelectric Spectrophotometry," J. Opt. Soc. Am. 40, 149-152 (1950)