Abstract
FG Sagittae is a peculiar variable star that shows changes in abundances of the rare earth elements and the cooling effect. For these reasons, we have been observing FG Sge since 1975 at the Dominion Astrophysical Observatory, Victoria, with a spectrograph giving a dispersion of 15 A mm -1 the blue region. The cooling effect in the atmosphere of FG Sge has been estimated by three different methods: i) from the intensity ratio of absorption lines; ii) from the values of the blanketing coefficient in the interval 4525-4950 A, and ill) from the energy distribution of the continuum. Ml the methods have given consistent results. The spectrum of FG Sge did not change considerably during the period 1975-1980, and it seems to be close to KO lab in spectral type. One can see this in Figure 1 which shows the comparison of the spectra of FG Sge and Ia supergiant stars.
