I am going to start with the premise that planetariums serve several roles in their communities:

1. They are popularizers of astronomy and space science

2. They support and enhance the teaching of astronomy and related subjects within the formal education system

3. They provide a community resource for astronomical information

Not all planetariums incorporate all of these roles or do so to the same degree.

Planetariums, as facilities, come in a variety of forms. At one extreme might be a space theater with its wide-format films. A major public facility would have a strong emphasis on public shows and school programming. A college or school facility would emphasize programming for the education system at some or all levels with some or no public programs. At the other extreme would be the small portable planetariums with 100 per cent use for school activities.