The “terminator” in this case is not some sci-fi sounding robotic killer. Instead, it is the line that marks the sunlit from the dark part of the moon. As it moves across the moon’s surface each month it has a dramatic effect on what is visible.
Here, for example, is Tycho crater, taken on 11 April.
Tycho is the centre of the large “splash” in the middle of this photo. Large rays of ejected material, resulting from the impact that caused the crater, are clearly visible, extending over a thousand miles in all directions.
Yet when we look at the same crater a few days earlier, the scene is completely different.
Tycho is more to the left in this picture. The rays are much less pronounced, with some of them barely visible. Instead, the crater walls and central mount are much clearer. These two photos barely even look like the same moon.
As I’ve pointed out before, even over a single night, the terminator moves visibly across the moon’s surface. It is this constant interplay of light and shadow that makes photographing the moon so endlessly fascinating.
You can read more about Tycho crater on Wikipedia.
Platitude of the Day 