The Distortion of Film of the Astronomical Plate

Abstract

The distortion of the astronomical plate is studied by means of apparatus which was constructed for our purpose to measure the displacement of star image.
The measurements were made for four hundreds and one plates. The value of distortion, which is defined as σ=Δl/l₀is obtained for x- and y-coordinates as follows:
σx=3.0×10^-5±2.1,
σy=2.0×10^-5±2.1.
The close correlation is found between the humidity during the observation and the distortion. The correlation coefficient between them is calculated as -0.75.