Twenty years of the Gunma Astronomical Observatory, experimental trials of how to use a 1.5-m telescope at a public observatory

Gunma Astronomical Observatory (GAO) is regarded as a pioneer of the public observatories equipped with a large telescope of far beyond one meter class. It was established in 1999 by Gunma prefecture local government. Its main telescope is a 150-cm reflector which has an eyepiece system for the star gazing by public people in addition to advanced measuring instruments such as a very powerful high resolution spectrograph for the scientific research. Using this telescope we have carried out a number of activities and studies in the fields of scientific research, education and public outreach. Many of them were kinds of experimental trials of how to use such a telescope at a public observatory. We present some examples of our experiences in these two decades.