1. Armagh Observatory and Planetarium , College Hill, Armagh BT61 9DB , UK
2. Institut für Physik und Astronomie, Universität Potsdam , Haus 28, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam-Golm , Germany
3. Dr Karl Remeis-Observatory & ECAP, Friedrich-Alexander University Erlangen-Nürnberg , Sternwartstr. 7, D-96049 Bamberg , Germany
4. South African Astronomical Observatory , P.O. Box 9, Observatory Rd., Observatory 7935, Cape Town , South Africa
5. Department of Astronomy, University of Cape Town , Private Bag X3, Rondebosch 7701 , South Africa