1. Royal Observatory of Belgium , Ringlaan 3, B-1180 Brussels, Belgium
2. National Astronomical Research Institute of Thailand , 260 Moo 4, T. Donkaew, A. Maerim, Chiang Mai 50180, Thailand
3. Thüringer Landessternwarte , Sternwarte 5, D-07778 Tautenburg, Germany
4. Department of Physics and Materials Science, Faculty of Science, Chiang Mai University , Muang, Chiang Mai 50200, Thailand
5. Department of Physics and Astronomy, University of British Columbia , 6224 Agricultural Rd, Vancouver, BC V6T 1Z1, Canada
6. Institute of Physics, Karl-Franzens University of Graz , NAWI Graz, Universitätsplatz 5/II, A-8010 Graz, Austria