Adrian Dening's Stars Over Somerset

Wednesday, 21 May 2025 16:42

Monday 26th May to Sunday 1st June 2025

On Tuesday 27th we have a New Moon, when the entire surface of the Moon that faces us is in shadow. By Saturday 30th, it will have become a thin waxing crescent shape, as just a little bit of the surface facing us is illuminated by sunlight.

If you venture outside just after dark on the Saturday evening, say around 11pm, the crescent Moon will be setting towards the west north west, with planet Mars to the left of it, due west.

Because the Moon takes the same amount of time to orbit around us as it takes to rotate on its own axis, the same face of the Moon is always pointing towards us. Some lunar features like the crater Tycho and the Sea of Tranquility are always visible when the surface is illuminated. You can also identify the locations of all the Apollo Moon landings as no missions attempted to explore the "dark side of the Moon".

As it orbits around us, the Moon does experience a phenomenon known as "libration" or in other words, it wobbles a bit! This means that sometimes you can see a little further around the western or eastern limbs of its surface.

On Saturday 30th, libration favours the eastern edge and you should be able to see the Mare Marginis and Mare Smythii that are about 360Km and 200Km in diameter respectively.

Unlike most seas or "mare", Marginis has an irregular outline and small features that are thought to be the result of impact craters being covered by lava. Of course, you will need a telescope to see such detail.