along Potash Road at sunrise this morning, celebrating a clear dawn for witnessing a most impressive solar alignment between a shadow line and ancient rock art.
Predawn on the frazil ice-covered Colorado River.
Our inspirational leader, Rory Tyler. Link to his presentation on The Potash Panels - Frontiers in Rock Art Analysis.
Panel showing spirit bear paw petroglyph (half in shadow on the left) with the winter solstice shadow aligning perfectly with scribed lines on the sandstone.
Wider view of the panel, with the vertical rib of rock serving as the gnomon shown illuminated on the left.
Annotated non-sunlit image of the panel showing highlighted dotted line A that follows a scribed line on the petroglyph of the spirit bear claw that corresponds to the shadow cast during the winter solstice. Color differences seen here are due to variations in the desert varnish. There was undeniably an ancient astronomer at work here hundreds to a thousand years ago to have etched this precise line. Cool beans.
Screengrab from a GoPro time-lapse of the shadow line popping into place at the moment of solstice sunrise. Like I said, cool beans.