18.6 years is period of the lunar orbital nodes' regression around the ecliptic. Maybe this is what they meant. Mark Nicol ----- Original Message ----- From: Hank Williams To: Utah - Astronomy Sent: Monday, April 29, 2002 9:31 AM Subject: [Utah-astronomy] Archae - Astronomy I received the message below from a friend in Arizona. I tried to put moon cycles (both earth viewed and star viewed) into the 18.5 or 9.25 cycles on the petroglyph, but neither worked out to whole numbers. So, I'm stumped, but thought the great minds of this group could probably come up with an answer. Thanks!! Hank Williams ------------------------------------------------------------------------------------------------------ I have a question to test your knowledge of astronomy. Last week when we were at the Hopi Reservation petroglyph site, the guide was showing us various places among the over 15,000 petroglyphs and where the old cultures would track the equinox to help them with spring planting. There was one location where he said they tracked the moon. The total cycle ran 18.5 years where it showed 9.25 years from one location to its outer most point and then 9.25 years back to the same location on the rock...a total of 18.5 years. Again, this what the guide told us. Does this make sense to you? Have a nice day. Regards, Dennis