1. Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
2. Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK
3. School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
4. Physics & Astronomy, University of Leicester, 1 University Road, Leicester LE1 7RH, UK
5. Astrophysics Group, School of Physics, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
6. Department of Physics and Atmospheric Science, Dalhousie University, Halifax NS B3H 4R2, Canada
7. University of Nottingham, School of Physics & Astronomy, Nottingham NG7 2RD, UK
8. Department of Physics, Virginia Tech, Blacksburg, VA 24061, USA
9. Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
10. Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany
11. Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala, Sweden
12. Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, ul. Słoneczna 36, 60-286 Poznań, Poland
13. Department of Physics and Astronomy, 6224 Agricultural Road, University of British Columbia, Vancouver V6T 1Z1, Canada
14. Gemini Observatory, Northern Operations Center, 670 N. A’ohuku Place, Hilo, HI 96720, USA
15. Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, the Netherlands