  A method for determining the effective temperature Teff of G- and K-type
giants and supergiants is proposed. The method is based on the use of two
photometric indices free from the interstellar absorption influence: the Q
index in the UBV photometric system and the [c1] index in the uvby system.
Empirical relations between the Teff values found for nearby and bright G- and
K-type giants and supergiants with the use of the infrared fluxes method
(IRFM), on the one hand, and the observed Q and [c1] indices for these stars,
on the other hand, are plotted. A systematic discrepancy between the
dependences of Teff on Q for the stars with standard and reduced metallicities
is found. Approximating the plotted dependences with second-order polynomials,
one can obtain a relatively simple and a rather accurate method for determining
the Teff value in the range of 3800 < Teff < 5100 K (based on the Q index) or
4900 < Teff < 5500 K (based on the [c1] index).
