A section of Chaco Canyon National Historical Culture Park, NM, that
has been occupied by both Anasazi and Navajo peoples, is being surveyed
for astronomically relevant features by Ambruster and A. Hull (OCA
Applied Optics). Particularly evocative is the Navajo name for this
area, which translates as sun moving across petroglyph. In
December 1995, they confirmed a winter solstice alignment at an
exceptionally rich early Navajo rock art site. Measurements from field
work the previous summer had suggested that the winter solstice sun
would rise in a 
formed by the visual intersection of a cliff on the
distant southeastern horizon and a large foreground boulder containing
two incised sun shields. This cliff, which is coincident with the
winter solstice sunrise azimuth, is the most conspicuous horizon feature
seen from this part of the canyon. Calculations further suggested that
the sun would ascend along the ridge of the foreground boulder, which
slopes upward at a 
angle from the horizontal. The
actual sun at winter solstice performed as the measurements had implied,
both in its rising position on the horizon, and in its slow march up the
ridge of the boulder. It is not clear whether the important thing for
the early Navajo observer was watching the morning sun ascend the
boulder or, for the sake of eye comfort, keeping the rising sun just
below the crest. However, the sky-related rock art (two sun shields,
plus several drilled constellations) on the same panel with incised
sacred (Yei) figures, strongly suggests the winter solstice sunrise was
noted and commemorated here.
Further work at the site includes mapping the locations of the major rock art surfaces, tying these measurements into a local geodetic marker, and following up several other potential alignments with important solar risings and settings. We are grateful to Dabney Ford, Chaco archaeologist, for research permits and access to the sites.