At the ninth “Oxford” International Symposium on Archaeoastronomy, held in Peru in January 2011, a paper carrying the title 'The sun and 15 doorways of Phnom Rung' was presented for the audience.

     By a mistake the paper carries my name as co-writer; but the content does not express my opinions about Prasat Phanom Rung and was not written in corporation with me!

     My view on eventual archaeoastronomical significance of Prasat Phanom Rung can be read in an article published in 2007 in vol. 33.2 of the Mueang Boran Journal.
     The article was published four years ago and I have no additional remarks, except that I have now completed a GPS-based field-survey on orientation of some 300 Khmer temples in NE  and E-Thailand, which will be published later this year. The broad picture is that nearly all temples are orientated allowing the rays of the rising sun to enter the eastern gate of the temples. One half of the temples are orientated towards true east (as for example Prasat Sdok Kok Thom and the royal temples at Angkor); the other half have orientations towards north-east (as for example Prasat Phanom Rung). Only a few temples are orientated 5.5 degree from true east. No temples are orientated towards the rising sun at either of the solstices.

     In the article in Mueang Boran Journal I tentatively conclude that if the orientation of Prasat Phanom Rung has archaeoastrological significance, then the astronomical event is not merely solar; but solar-lunar: The time span from the sunset aligned with the structure in March to the associated sunrise in April equals one tropical lunar month. This can be evidenced by observation: After having observed the sun set aligned with the 15 doorways of the temple then wait until the moon is visible and note the moons location among the stars. The moon changes location every night in a 27.3-days circle, called a tropical lunar month. When the moon in April has returned to the position noted in March, then the sun will rise aligned with the structure in April.
     The time-span between the two associated solar-lunar events is app. plus/minus14 days from equinox. And as there annually are two equinoxes, then there are be two sets of solar-lunar events every year.
     Seen by the eyes of a modern astronomer this is beautiful; but we do not know, if it was intended and observed by the ancient Hindu master-builders! If interpretation of inscriptions or other evidences could confirm that the solar-lunar events were intended, then Prasat Phanom Rung deserves a high rank among international archaeological landmarks.