Sydney Observatory is a museum of astronomy and a public observatory. It is Australia's oldest existing observatory and is now a branch of the Powerhouse Museum, the largest museum in the southern hemisphere. With 65,000 visitors each year, the observatory is popular with the public. Visitors can come during the day to see exhibits and audiovisuals and in the evenings on telescope viewing sessions. They can also take part in school holiday workshops, adult education courses or a telescope-making course. In addition, many school groups come along during the school terms to extend the astronomical knowledge of their students. Other professional services provided by the observatory include an annual guidebook with up-to-date information for the sky as seen from Sydney and an astronomical information service for the public and the media.