1. Astronomical Observatory of Padova, Asiago Section , Osservatorio Astrofisico, I-36012 Asiago (Vi) , Italy
2. Nayoro Observatory , 157-1 Nisshin, Nayoro, Hokkaido 096-0066 , Japan
3. Institute of Nature and Environmental Science, University of Hyogo , 8-2-1 Gakuen-nishi-machi, Nishi-ku, Kobe, Hyogo 651-2197 , Japan