1. LUTH, Observatoire de Paris, PSL Research University, CNRS, Université Paris Diderot, 5 place Jules Janssen, F-92190 Meudon, France
2. Armagh Observatory, College Hill, Armagh BT61 9DG, UK
3. Kuffner-Sternwarte, Johann Staud-Strasse 10, A-1160 Wien, Austria