Astronomy was well known to the Hindu people of India thousands of years ago, and this was revealed by the discovery of various astronomical aspects of several ancient Hindu structures. Outside India, e.g., the builders of Angkor Wat, a famous Hindu temple located in Cambodia, also integrated some aspects of astronomy into its design. In Central Java, Indonesia, the Prambanan Temple (which is older than Angkor Wat), is the country’s largest Hindu temple and may have the same claim. Previous research has suggested a relationship between Prambanan and astronomy, which is shown by the fact that it is oriented towards the cardinal points. This choice of orientation must have been made through consistent observations of the Sun. It also has been proposed that the construction of Prambanan applied the mandala principle, which is the basic concept for the construction of Hindu temples in India. This concept provides essential information regarding astronomy and its historical facts. For example, the date of establishment of a temple can be inferred from the mandala set up. From the type of mandala, it can be determined for whom the temple was built. Accordingly, our study examined the possibility of astronomical alignments between Prambanan and the Sun as well as the Moon. We suggest that apart from its religious functions, the Prambanan Temple may also have been used for lunar observations.