A scheme, based on the expansion of solar oscillations into spherical harmonics, for the identification of sectorial modes of intermediate degree in the interval l = 3-20, is presented. In this range, the frequencies of modes with similar quantum numbers can be very close together, so that a careful spectral analysis of their spatial pattern is needed effectively to separate these modes. The filtering scheme proposed is intended to operate on quantized images of the sun and reaches satisfactory resolving power by a two-step procedure, namely a straightforward filtering followed by the resolution of a system of linear equations. The results obtained are also shown to be independent on the ecliptic longitude of the earth.
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