Adrian Dening's Stars Over Somerset

Wednesday, 17 May 2023 17:00

Monday 22nd to Sunday 28th May 2023

Venture outside just after dark, say around 10pm, on Wednesday 24th and there is a great viewing opportunity if you look towards the west. A 25%-lit waxing Crescent Moon will be just above planet Mars. Mars has a magnitude of around +1.5 at the moment, so it will be easy to spot with the naked eye and it has an obvious reddish tint.

Looking to the right of the pair and a bit further down, Venus is still spectacular, shining very brightly. If you aim even a small telescope at Venus, it is possible to see its phase and the planet currently appears to be about 50%-lit or in other words, it will look like a tiny Quarter Moon.

The evening of Saturday 27th is a chance to spot one of the Clair-obscur lunar visual effects in your telescope - the Stars of Aristillus. The effect is caused by sunlight reflecting from the peaks in the middle of crater Aristillus. The whole crater is only 55Km in diameter and it is estimated to be over 1.1 billion years old! Around 10pm, the Moon will be located towards the south west and I have provided a diagram to help you locate the crater, which will be on the sunlight terminator, a little above the centre of the Moon's face.

Around this time of year is the start of the Noctilucent Cloud season. These night-shining clouds are caused by ice crystals in the upper atmosphere scattering light during astronomical twilight, so are viewable towards the north west horizon for up to a couple of hours after sunset. Similarly, they can be detected a couple of hours before sunrise if you are looking towards the north east.