Concept of the Celestial Sphere is arguably one of most difficult concepts in introductory astronomy. A physical, three-dimensional model is one of the more effective ways in helping the learning to visualize this concept. However, such model are often expensive and bulky. Here we propose a novel solution: a beachball. An algorithm is used to transform equirectangular vector graphic map into 6-gore cassini projections centered around 6 meridians. As a result, we now have a celestial sphere that only cost 10 USD and collapsible (with beach volleyball being a welcome side benefit!). The same algorithm can also be used to produce 12-gores version that can be printed on 3 sheets of A4 paper that can even be assembled without a single adhesive.

Biography:

Matipon Tangmatitham is a science communicator at the National Astronomical Research Institute of Thailand. He also serves as the director for International Training Centre in Astronomy under the auspices of UNESCO (ITCA). Although coming from background of theoretical cosmology, he now specializes in coming up with new activities to be implemented in Thailand and overseas via ITCA's Teacher Training Program.