David Purcell – Seasons in the Sun: Experimental Time-lapse Photographic Documentation of Archaeoastronomic Sites

 Previous documentation of petroglyph panels with apparent archaeoastronomical associations at Horseshoe Mesa (WS834) in Wupatki National Monument, Arizona, raised questions about the recording methodologies. The solar effects had been documented only on solstices and equinoxes, using tightly cropped still photographs, “freezing” a moving event and removing the interaction from the context of the panel. This project sought to test the validity of this common approach by recording the daily sun and shadow interactions on petroglyph panels 39 and 50 at Horseshoe Mesa using timelapse cameras. Daily recording for an entire year has apparently not been attempted previously in archaeoastronomical studies. Doing so would potentially confirm solstice and equinox interactions by demonstrating that the interactions are unique to those days or peak in intensity on those days, identify other possible commemorations such as cross-quarters days, and provide an expanded field of view of the known interactions. This experiment also evaluated the feasibility of daily timelapse photography of rock art sites, tested low cost equipment, and evaluated the role that weather might play in interactive solar displays. Data for seven specific research goals were collected. We conclude that Panel 39 does mark the solstices and not the equinoxes as previously documented, and does not provide any additional archaeoastronomical activity, but may indicate whole seasons rather than specific dates. Panel 50 exhibits five solar interactions, two of which are coincidental to the placement of the petroglyphs, and three interactions are intentional petroglyph associations with natural shadow and sun phenomena.