Okanagan early risers are familiar with the spectacle of light from the rising sun descending our western mountains before it reaches the valley floor. The same phenomenon on the moon creates amazing scenes that reveal huge contrasts between rugged relief and lowlands -- rarely demonstrated more vividly than on the evening of May 10/22 as sunlight illuminated the Jura Mountains -- the high rim of Sinus Iridum. When I first saw it, more than half of the 260-km diameter bay was in shadow and the arc of the mountains was far from complete. Over the next hour and a half, the gap gradually filled in with points of light and tiny squiggles -- sunlight on ridges and hilltops. Given the moon's slow rotation (and sunrises), it would take about half an earth day for sunlight to cover the floor of Sinus Iridum. The accompanying images are cropped from cell phone shots taken through the eyepiece of a 12" f/4.9 Dobsonian.