to observational technique including the making of various astronomical lenses and
small telescopes. Yamamoto and Nakamura started photographic and spectroscopic
observations. They collected around 2000 plates for stars and solar system objects up
to 1930. These data included 90 spectrograms of 40 stars in various spectral types
from B to M types and from luminosity classes I to V. From its rather homogeneous
distribution of stars on the HR diagram, the purpose of observations might have been
to produce a spectral atlas of bright stars, but the program was not implemented due
to the premature death of Nakamura in 1932 at age 29 (Tomita and Kubota 2000).
In 1929, Kwasan Observatory was newly established at the summit of Mount
Kwasan. Yamamoto served as the first director until his retirement in 1939 (Fig. 4.8).
Fig. 4.7 Photographic period-luminosity curve. Ordinates are apparent magnitude; abscissas are
logarithms of the periods. Crosses indicate measurements by Leavitt (1912) and dots by Yamamoto.
(Shapley et al. 1925)
4.1 Yamamoto Issei and Variable Stars
87