The Variable star S Persei
(021558) was discovered by A. Krueger in 1872 (Krueger, 1874) and it has been
theobject of regular observation for more than ninety years, beginning in 1880.
S Persei is listed in the 1969 GCVS as an SRc variable of spectral and
luminosity types M3eIa-M4eIa, which is to say, a red supergiant with
semi-regular variabiltiy. Figures 1(a) and 1(c) show the visual light curve of
S Persei from 1880 until early 1974, after 1911 being based on AAVSO
observations for the most part. Inspection of the light curve indicates that S
Persei has distinctly cyclic light oscillations of greatly varying amplitude.