systematic errors are present in the data, this procedure causes the significant improvement of the sample regularity and causes the increasing of an estimation efficiency. At the same time if the excluding process significantly changes the estimated parameters, it may be a strong reason to assume the data is not regular, and consequently may indicates that it is necessary to use some type of procedure to reduce the irregularity.

It should be noted that using data reduction methods which break a spatial harmonics orthogonality causes a certain spectral smoothing and may reduce or even may camouflage the abnormal amplitudes. In this situation the risk of missing a really existing anomaly is run, and the signal estimation process may be accomplished with some additional errors.

The data reduction procedure we propose is the following. We use COBE A and B channels (Wright et al., 1994a) and produce the sum and the difference radio-maps as a half-sum and a half-difference of the A and B maps respectively. All data on the sum map are a sum of a signal and a noise. All data on the difference map are only the noise, the signal amplitude is zero.

We exclude from the sum 