1. Astronomy Section, Nagoya City Science Museum , 2-17-1 Sakae, Naka-ku, Nagoya, Aichi 460-0008, Japan
2. Department of Physics, Graduate School of Science, Nagoya University , Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
3. Institute of Astronomy, The University of Tokyo , 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan