1. Armagh Observatory and Planetarium , College Hill, Armagh BT61 9DG, UK
2. Institut für Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Universität Tübingen , Sand 1, D-72076 Tübingen, Germany
3. Department of Physics & Astronomy, University of the Western Cape , Private Bag X17, Belville 7535, South Africa
4. Australian Astronomical Optics, Faculty of Science and Engineering, Macquarie University , North Ryde, NSW 2113, Australia
5. Department of Astronomy, University of Cape Town , Private Bag X3, Rondebosch 7701, South Africa
6. South African Astronomical Observatory , P.O. Box 9, Observatory, Cape Town 7935, South Africa