New Proper Motions for HIPPARCOS Stars

Extract

During the preparation of the Hipparcos Input Catalogue precise positions were measured very recently by the Bordeaux automatic meridian circle (BMC) for about 5500 stars in the northern hemisphere. On average eight observations were made for each star at a mean epoch 1987. The estimated mean error in α is 0″.12 and in δ 0″. 18. With 2555 stars almost half the BMC sample lies in the declination zone -2° < δ < +32°. In this zone the (x,y) measurements of all Astrographic Catalogue plates have been newly reduced (S. Röser, priv. comm.). So, at least two independent positions are available for practically all stars down to the limiting magnitude of the AC with epochs around 1910 and with a mean positional error of 0”. 28. A combination of these two sources should provide proper motions to an accuracy of 0″. 004 yr⁻¹.