Some results of expanded data analysis derived with a prismatic astrolabe in Poltava are discussed. The information potential of initial observational data is studied. The method of the «contacts dispersion» is used for restoring the pattern of the maintenance of a star in every action of its registration. In the diversity of patterns, a few typical scenarios are recognized depending on dominant factors of instrumental, atmospheric or personal origin. The method of «reference moments» is developed which is effective for elimination of some instrumental and personal errors. We outline some approaches to study of complex structures in order to identify dominant factors of distortions and to evaluation of their influences.