In order to compute the vetrtex using the most probable cluster members selected from Platais et al. (2003) , we used apex diagram method (AD-method). This method has been used and explained in detail by Chupina et al. (20 01, 20 06 ) and Vereshchagin et al. (2014) . AD-diagram, plotted using individual apexes of stars represents the distribution of stars in the equatorial coordinate system.
The coordinates are obtained from the solution of a geometrical problem in which the coordinates of the points of intersection of the vectors of spatial velocities of stars are displaced observation points with the celestial sphere.