Lunar Libration

December 05, 2010

Photographer: Manuel Castillo Vela
Summary Author: Manuel Castillo Vela; Jim Foster

Though the Moon always keeps the same face toward the Earth, we don't always see the same amount of the lunar surface. Of course, the lunar phase changes from one night to the next, but libration (wobbling effect) also comes into play. This can be seen above. Both the left image (photographed on September 30, 2010) and the right image (photographed on October 15, 2010) are approximately equally illuminated. On September 30, the Moon was in a waning gibbous phase, while on October 15 it was in a waxing gibbous phase. Notice that the full face of the Moon can't be merged or fixed since the inner edge of each image shows the same craters -- the two images don't exactly line up. Diurnal libration is the small daily oscillation that occurs due to the Earth's rotation. As the Earth rotates, an observer on the surface is carried to one side and then to the other of the line connecting the center of the Earth and the Moon. This permits us to see a bit more of the Moon than we could if the Earth wasn't spinning on its axis. Over time we can see about 59 percent of the Moon's surface. Photos taken from Chiclana de la Frontera, Spain.

Photo Details: Benq DC Digital Camera: T850 Refractor Telescope; 700/70/20 mm; Photoshop - CS 4 + Virtual Moon Atlas 5.0