To find the distance of open star clusters other methods have been developed. The method of diameters is: if "D" is the diameter of the cluster in parsecs, and "d" is its angular diameter in minutes (‘), we have D=r.sin (d’), where "r" is the distance to the cluster in parsecs. Then r=3438.D/d’. "D" is got from a classification of the intensity of concentration of the stars to the centre and the location of the bright and weak members. The clusters from given class have the same diameters. The members of some open clusters have independent visible motions, which are directed towards a single point. We can find the distances to such clusters very accurately. Using this method the distance to the Hyades is 36 pc=118 l.y..