International Journal of Astronomy and Astrophysics, 2015, 5, 267-274 Published Online December 2015 in SciRes. http://www.scirp.org/journal/ijaa http://dx.doi.org/10.4236/ijaa.2015.54030 How to cite this paper: Gebrehiwot, Y.M., Tessema, S.B. and Malkov, O. (2015) Study of Principal Catalogues of Visual Double Stars. International Journal of Astronomy and Astrophysics, 5, 267-274. http://dx.doi.org/10.4236/ijaa.2015.54030 Study of Principal Catalogues of Visual Double Stars Yikdem Mengesha Gebrehiwot 1 , Solomon Belay Tessema 2 , Oleg Malkov 2 1 Astronomy and Astrophysics Research Division, Entoto Observatory and Research Center (EORC), Addis Ababa, Ethiopia 2 Institute of Astronomy, Russian Academy Sciences, Moscow, Russia Received 24 November 2015; accepted 17 December 2015; published 22 December 2015 Copyright © 2015 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract The goal of this study is to develop a tool for detection of errors and misprints in principal cata- logues of visual double stars. Modern statistical investigations of visual doubles (which are about 130 thousand, and they represent the most numerous observational type of binaries) are based almost exclusively on data, listed in those catalogues. So their correction is a challenging task, otherwise the statistics of visual binaries can be biased. Study of individual stars should also be based on correct data. We have presented tools to detect some of errors in the catalogues, espe- cially, to indicate cases i) when positional information on components of a pair is contradictory, and ii) when a double star or its component is included in a catalogue twice, under different names. Keywords Visual Binary Star, Positional Inconsistency, Data Duplication, Reference Coordinates, Additional Component Coordinates 1. Introduction Heggie in his investigation of formation and evolution of binaries identified two classes of binary stars [1]. He called these binaries as “soft” and “hard” binary stars. Actually this classification is analogues to “wide” and “close” binary stars respectively. There is no well defined boundary between close and wide binary systems. It differs from author to author according to the purpose and types of the data required. The operative parameter of a binary system is the semi-major axis a. Since its values vary over a wide range of several orders of magnitude, the exact form of semi-major axis distribution is not well known yet. According to [2]-[4] binary stars can be