Modern Environmental Science and Engineering (ISSN 2333-2581) March 2021, Volume 7, No. 3, pp. 195-201 Doi: 10.15341/mese(2333-2581)/03.07.2021/002 Academic Star Publishing Company, 2021 www.academicstar.us Research on Astronomical Orientation in the Greek Temples Using Solar Analysis Software: The Parthenon as a Case Study Ezequiel Uson Guardiola, and Carles Guillen Amigó School of Professional & Executive Development, UPC, Barcelona, Spain Abstract: The aim of this research was to analyze the astronomical orientation of Greek temples and the relationship between that and the religious rituals carried out in them, using solar analysis software tools. For our case study, we chose the temple of the Parthenon. Highly practical solar analysis software tools enabled us to determine the astronomical azimuth of the building’s main longitudinal axis with a high degree of accuracy and to simulate the manner in which solar radiation was allowed to penetrate the innermost areas of the sanctuary. We also calculated the intensity of natural lighting entering the building and the time of year when this would have happened. The methodology applied in this research could be extrapolated to undertake similar analyses of other Greek temples. Key words: astronomical orientation, solar analysis software tools, the Parthenon, Panathenaea Festival 1. Introduction One of the most potent tools that the Ancient Greeks developed and exploited was solar geometry. As already widely reported by other authors, the Ancient Greeks achieved a high level of astronomical precision that allowed them to lead the development of solar architecture. Their knowledge of the path of the sun, in the different seasons of the year, allowed them to choose the most appropriate orientation when laying out new settlements and designing significant buildings [1]. In addition, their sophisticated geometric knowledge helped the Ancient Greeks to accurately determine the astronomical orientation of their sanctuaries and temples. Such astronomical observations were also fundamental to the celebration of religious rituals in honour of the deities to which sanctuaries, and the main temples within them, were Corresponding author: Ezequiel Uson Guardiola, Dr., Professor, research areas: sustainable architecture, climate and energy buildings simulation software. E-mail: ezequiel.uson@upc.edu. dedicated. These celebrations would usually take place on a set day of the year. It was important to ensure that such festivals were held on the correct day and that the calendar did not move out of season. However, it is not unreasonable to expect that Greek architects working more than two thousand years ago, and who would have had only basic topographic tools and trigonometric calculations at their disposal, could have made errors of several degrees in their astronomical alignments. This has, in fact, been demonstrated by recent examinations using modern instrumentation. 2. The Astronomical Orientation of the Greek Temples Greek temples were generally built facing Eastwards. In an analysis of 113 temples previously studied by Heinrich Nissen (1910), William Bell Dinsmoor (1939) discovered that approximately 73% were oriented within 60º of due east, 8% within 60º of due west, and 19% in other directions [2]. Dinsmoor’s general conclusion about the orientation of Greek temples was that their positioning was determined by the need to