http://www.nbcnews.com/id/31952662/ns/technology_and_science-space/#.UR23_KWtx2A I was thinking something like that, and I think this goes along your same line of though (Ptolmic model saw stars rotating around the earth, while this chart is made for stars that appear to be rotating around the moon). The article says that this was used by the crew of apollo 11 to determine where on the moon they landed. Since the back ground of the chart is a map of Puerto Princessa maybe instead of overlaying the chart with the land map of Puerto Princessa we should see if we can overlay the map with with a chart of the night sky of Puerto Princessa. Also as another tidbit of information, I saw earlier today on a travel site they claimed that Puerto Princessa has a clear night sky due to it being close to the equator