Observational studies of the solar cycle at the National Astronomical Observatory of Japan

Instrumentation for observational studies of the solar activity cycle, using ground-based optical telescopes at the National Astronomical Observatory of Japan, is described. A newly-built 10-cm telescope for sunspot observations is explained in detail. A future instrumentation plan for long-term studies of the sun, called the Solar Cycle Telescope, is presented. This will be composed of a 30-cm Makustov telescope equipped with an infrared Stokes polarimeter, and a 15-cm refractor for precise Doppler-shift measurements.