CH Cygni Half a Century Ago – Changing Activity of the Cool Component

CH Cyg was observed visually by Professor Władysław DziewulsKi in the years 1930–1940 at the Vilno Observatory, with the 15 cm refractor using Argelander’s method. As a sKillful and experienced observer he achieved the accuracy of his single measurement of about 0.05 mag. The series of his 652 estimates of CH Cyg has been recently reduced and is discussed in this paper. Apparently in those years the star was in relatively quiet state (like in the years 1970–1977), when in the visual region the light of only the red giant component of this binary is visible. We deduce it from: a) absence of any emission lines in spectra taKen by A. Joy in 1930 (Joy 1942) b) visual brightness of the star almost never exceeding 7.0 mag. what is typical for the quiet state of pure M6III spectrum c) red color, resulting from comparison of our visual brightnesses and the photographic ones published by S. Gaposchkin (1952)