The Image of the Month for September highlights the changes we see to the surface of the Moon during the different phases. This animation shows the same section of the Moon on two different nights, just 3 days apart (25 September 2015 - 21:18 GMT and 28 September 2015 - 22:36 GMT). The Moon is moving towards the stage of full Moon, where the entire surface, as viewed from Earth, was illuminated by the Sun. This happened on the 28^th September, in the second of the images. Three days earlier the Moon was at it's waxing gibbous phase, where waxing refers to the Moon getting brighter , on the way to the Full Moon phase, and gibbous is the phase between half and full, where almost 75% of the Moon's surface is lit up. On the first of the images, at the gibbous phase, we can see much more detail on the surface, caused by shadows being cast from the craters, valleys and mountains on the surface. When the Moon reaches full, the sunlight falls directly onto the surface, much like the Sun being overhead on midday, so the shadows cannot be seen - this means we lose the information about which features are high off the ground, and the whole surface appears to be smooth.