The structure of proper-motion diagrams for nearby stars

The structure of the proper-motion diagrams for an ensemble of nearby field stars is analyzed using a simple model. For comparison, the observed proper-motion diagram is constructed using data of the Hipparcos catalog. A complete description is given of the modification of the van Altena method, which allows stars with similar space motions to be identified based on their proper motions. In the original version of this method, the stars had to be located within one-quarter of the celestial sphere, whereas our version is free of this restriction.