3. Yerkes Observatory (1988)

Yerkes Observatory, at Williams Bay near Chicago, is a most unusual place. Its main telescope is not a reflector, but a refractor - the world's largest Old-fashioned though it may look, Yerkes is in the forefront of scientific research, as Patrick Moore explains when he goes there to talk to the director, Dr Al Harper, and members of the observatory's staff.

Release date: 1988-03-30