Tue 13th May was a full moon. It was quite difficult to photograph because it was so low in the sky. There was only a brief window of about half an hour where it could be seen between my house and next door’s. To make matters worse, it was a very cloudy night, with only occasional gaps in the clouds. So I waited patiently and was rewarded with a brilliant orange coloured moon.
The picture on the right hand side was the result.
The moon on the left was taken on 15th Dec last year. They were both taken with the same camera, same telescope, same settings and resolution. The pictures have been cropped by the same amount. And no, you’re not imagining it, the May moon is smaller. But why?
At the risk of sounding like Father Ted, the May moon is smaller because it’s farther away. In fact it’s 10% farther away than the December moon, and consequently is 10% smaller. The moon orbits the Earth in an ellipse. These two pictures show a full moon at its closest and farthest points. The following picture illustrates this even more starkly.
But size and colour aren’t the only differences. If you look at the top of the moon, it should be clear that they’re not showing exactly the same features.
The moon wobbles on its axis, making different features available at different times. This alters the exact face that the moon presents to the Earth throughout the year. Features that are invisible one month can suddenly become visible the next.
Taking pictures of the moon isn’t quite as boring as you might think.
Platitude of the Day 