Planetanya is part of the recently-opened Madarame Centre for Science, Space and Culture. Besides the planetarium and its space films, it also has observation telescopes and an activity garden for children. It's a good 2km walk from the city down Ben-Gurion Blvd, so it might be worth jumping in a taxi from town.
The entry price includes one film; additional films are 15NIS. The website is in Hebrew only.