Effect of Slit Width on Background Correction in Photographic Photometry

Abstract

Slope of the characteristic curve drawn from measurements of a narrow-lined spectrum is less than that of a curve drawn from broad lines or from continua This is due to. 1) the lateral diffusion of lines within the emulsion, 2) narrow lines being subject to Schwarzschild-Villiger Effect in the densitometer, which particularly tends to change the shape of the toe. (This effect is minimized in dense lines due to diffusion), and 3) the spreading of dense lines, which causes errors in reading background if the area read is too close to the line. Each of the three effects lowers the line-to-background ratio.