Astronomy Picture of the Day

Explanation: Who's watching whom? The featured image of the Moon through a gap in a wall of rock may appear like a giant eye looking back at you. Although, in late October, it took only a single exposure to capture this visual double, it also took a lot of planning. The photographic goal was achieved by precise timing -- needed for a nearly full moon to appear through the eye-shaped arch, by precise locating -- needed for the angular size of the Moon to fit iconically inside the rock arch, and by good luck -- needed for a clear sky and for the entire scheme to work. The seemingly coincidental juxtaposition was actually engineered with the help of three smartphone apps. The pictured sandstone arch, carved by erosion, is millions of years old and just one of thousands of natural rock arches that have been found in Arches National Park near Moab, Utah, USA. Contrastingly, the pictured Moon can be found up in the sky from just about anywhere on Earth, about half the time.