Astron. Astrophys. Suppl. Ser.
Volume 118, Number 2, August 1996
|Page(s)||277 - 282|
|Published online||15 August 1996|
The astrometric accuracy of “Carte du Ciel" plates and proper motions in the field of the open cluster NGC 1647
Sternwarte der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany
2 Observatoire de Bordeaux, BP. 89, F-33270 Floirac, France
3 Centre d' Analyse des Images, Bâtiment Perrault, Observatoire de Paris, 77 avenue Denfert Rochereau, F-75014 Paris, France
Send offprint request to: M. Geffert, Bonn
Accepted: 19 January 1996
The astrometric accuracy of triple image Carte du Ciel plates has been analysed using plates of the open cluster NGC 1647. A new multithreshold technique was used for the treatment of the triple image plates. Accuracies ranging from 100 mas to 200 mas were found. We determined proper motions with a median accuracy of 1.6 mas/a for 2220 stars in the field of NGC 1647. The membership probabilities of stars in the cluster region agree very well with the data of Francic (1989). Due to a significant difference of the proper motions of SZ Tau and the cluster members, SZ Tau seems not to be a member of NGC 1647.
Key words: astrometry / stars: individual: SZ Tau / Galaxy: open clusters: individual: NGC 1647
© European Southern Observatory (ESO), 1996