1. Department of Astronomy, Institute for Geography and Earth Sciences, Eötvös Loránd University, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary
2. Centre for Astrophysics and Space Science, Eötvös Loránd University, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary
3. Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly Thege Miklós út 15-17, H-1121 Budapest, Hungary