The wide neighborhoods of 401 open clusters are analysed using the the modern, high precision, homogeneous all sky ASCC-2.5 all-sky catalogue (Kharchenko, 2001, Cat. <I/280>). More than 28000 possible members (including about 12500 most probable ones) are identified using kinematic and photometric criteria. Star counts with the ASCC-2.5 and USNO-A2.0 (Cat. <I/252>) catalogs are used to determine the angular and linear radii of cluster cores and coronae, which exceed the previous published values by factors of two or three. The mean proper motions are determined directly in the Hipparcos system for 401 open clusters, for 183 of them for the first time. The heliocentric distances of 118 clusters are determined for the first time based on color-magnitude diagrams for the identified members.