  We investigate the applicability and accuracy of the iteration scaling
approximation, proposed by Kylafis and Bahcall (1987). It is shown, that while
this method provides results sufficiently close to the exact solution of
radiative transfer problem, care must be taken in cases when the distribution
of interstellar dust significantly differs from that of light sources. The
problem is successfully circumvented by using the ratio of scattered light
distributions obtained in the first two iterations.
