1. DiSAT, Universitá degli Studi dell'Insubria, Via Valleggio 11, I-22100 Como, Italy
2. INAF, Osservatorio Astronomico di Brera Merate, via E. Bianchi 46, I-23807 Merate, Italy
3. INAF, Osservatorio Astronomico di Roma, Via Frascati 33, I-00078 Monteporzio Catone, Italy
4. Department of Physics and Astronomy, Box 41051, Science Building, Texas Tech University, Lubbock, TX 79409-1051, USA
5. Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, NL-1098XH Amsterdam, the Netherlands
6. Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
7. Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, PL-00-716 Warsaw, Poland
8. New York University Abu Dhabi, PO Box 129188, Abu Dhabi, UAE
9. Department of Physics, Durham University, South Road, Durham DH1 3LE, UK