Circumstellar shell effect on near-infrared spectrum of chi Cyg

Spectral observations of the long-period variable of the chi Cygnus have been carried out in the range of 6500-8300 A with the minimum brightness in 1973. A relative energy distribution in the spectrum of the star has been obtained for this range. According to the absorption band intensity the spectral classification has been performed and an average dependence between the V-R and R-I colour indices and the spectral type through-out the cycle has been obtained. In the ascending branch of the brightness curve the star undergoes a considerable reddening, as compared to its spectral type, which can be explained by an increase of the circumstellar envelope at the minimum of brightness. The total visual absorption in the envelope accounts for 2sup(m)