A projection system having a set of projectors that cast images: (i) outwards onto the concave surface of a hemispherical dome, as is usual in planetariums and (ii) inward onto the convex surface of a centrally located sphere. The images thus cast may be coordinated by a controlling computer program, so that changes in the content or orientation of the images on the sphere result in corresponding changes in the images on the dome and vice versa.