Sky distribution (RA and Dec not in scale) of the Coma supercluster galaxies. Black dots represent the optically selected galaxies (all types) selected from the SDSS database (11^h30^m < RA < 13^h30^m, region 1) or from ALFALFA in the strip between 24° < Dec < 28° beyond the previous RA window (region 2). Red dots refer to the 261 galaxies observed in Hα3 in the ALFALFA strip. The 139 optically selected CGCG galaxies followed-up in Hα outside the ALFALFA strip and 16 in the ALFALFA strip are shown as blue dots.