After a hike trough the night I reached the arcs before sunrise, with the galaxy center just a little bit too high. The panoramic picture shows only 4 of the 5 arcs, as the 5th is in the ceiling and does not fit into an overall picture. The rocks above green river are lighted by the thin crescent moon and a little bit of LLLL, low level landscape lighting.

Edit: my mistake, the hole in the ceiling is the one on the right side. The 5th arc is between the big one and the hole on the right side. It is barely seen because of the rocks in the foreground...