Digital Planetariums for Everyone:
Astronomy Visualisation in Reflection

Abstract

The earliest telescopes were refractors made with combinations of glass lenses. They suffered from chromatic aberration and other optical defects, were difficult to scale to larger size (due to weight and cost limitations), and while providing better image quality and higher contrast (as there is less loss from a light path based on transmission that does not have to pass barriers such as secondary mirrors), they have mostly been supplanted by reflecting telescopes. This is because reflectors are generally cheaper, easier to construct and have fewer optical limitations e.g. although a highly polished surface is required to maximise reflectivity, there is no chromatic aberration.

With the aim of not pushing an analogy too far, jump forward nearly 400 years from the time of Lipperhey and Galileo to the new era of single projector digital planetariums. The current generation of lens-based fisheye solutions suffers some of the same problems of the early telescopes: chromatic aberration near the edge of the field, high-cost, and possibly scalability. Like Newton's revolution in telescope design, our recently developed MirrorDome uses light reflected from a spherical mirror to illuminate the dome, providing an affordable alternative that might change the way audiences experience planetariums in the future.

In this invited review on the future of the digital planetarium, we reflect on our experiences in astronomy visualisation from the fourfold position of astrophysics researchers, public educators, content creators and technology developers. While this paper may demonstrate a certain personal bias, we would hope that some of our ideas will be of interest to planetariums of all sizes, as more facilities are challenged by the question: when to go digital?