Moon Wobble
This time-lapse depicts a typical view from the northern hemisphere. The most dramatic monthly change is the moon’s phase, caused by the shifting angle of the sun as the moon orbits the Earth every 27 days. Also, due to the tilt and shape of the moon’s orbit, we see it from a slightly different angle over the course of a month generating a slight wobble or libration. Because of this we actually see more than half of the lunar surface over a month, about 59%.
The size differences you see are due to the orbit of the moon around the Earth being elliptical. The moon will appear larger when it reaches the closest point to Earth in its orbit or perigee, the opposite being apogee. The size differences are around 10% and when perigee also happens around a full moon, this creates a so called “Super-Moon”. Combine that sight with the Moon Illusion and you have - what seems like - an extremely large moon.
Via NASA
(via itsvondell)
