Adrian Dening's Stars Over Somerset

Thursday, 27 February 2025 17:00

Monday 3rd to Sunday 9th March 2025

The late evening of Tuesday 4th into the early morning of Wednesday 5th sees an unusual event - a chance to witness the shadows of two Galilean moons as they simultaneously transit across Jupiter's surface. Just before midnight, Jupiter will be located towards the west and the transits of Ganymede and Europa can be observed with your telescope until about 2am on the Wednesday morning.

Pop back outside and look to the west again around 10pm on the Wednesday evening to see Jupiter once more, with a 42%-lit waxing crescent Moon just to the right of it. The constellation of Orion will be to the left of the pair.

The Moon is "waxing" because it is heading towards a Full Moon later in the month on 14th.

Repeat the exercise around 10pm on Saturday 8th and the Moon will be higher in the sky and located more towards the south west. This time it will appear very close to planet Mars. The illumination of the Moon will have passed the "First Quarter" phase and you will now observe it as a 70%-lit waxing gibbous Moon.

This is the optimum time to spot the Clair-Obscur visual effect known as the "Jewelled Handle" on the Moon's surface.

In the art world, the technique known as "Chiaroscuro" refers to the use of strong contrasts between light and dark. In the astronomy world, the French translation of "Clair-Obscur" refers to extreme contrasts on the lunar surface where sunlight falling on the landscape produces obvious shapes at certain times of the month, when the Moon is in a particular phase and light from the Sun is hitting it at a specific angle.

www.starsoversomerset.com

Screenshots courtesy of Stellarium