Multi-Conjugate Adaptive Optics systems need a suitable configuration of Guide Stars surrounding and/or within the instrument field of view to perform the best correction of the atmospheric turbulence. The number of Guide Stars and its geometrical configuration influence the correction performance of the system. In the case of the MCAO demonstrator, no Laser Guide Stars will be used therefore the selection of science targets has to be based on the "natural" availability of such suitable Natural Guide Stars configurations (asterisms). In this paper we present the results of a systematic search for bright asterisms performed using the Tycho-2 catalogue. We discuss the selection criteria adopted to extract the best candidates and show a number of study cases. Furthermore a cross correlation with extended objects (e.g galaxies, nebulae,...) is presented in the framework of maximizing the scientific feed-back of the on-sky observations. Finally the preliminary results of the correlation between extended objects and fainter Guide Stars (down to the 16th magnitude) using the USNO A2 catalogue are shown.
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