Look out for the thin crescent of a waxing moon

If you want to spot a young and beautiful waxing crescent moon, tonight could be your lucky night, writes Ian Griffin.As the sun disappears below the horizon, our closest celestial neighbour will be just 2.7 days past new. At sunset, the thin lunar crescent will be twenty-five degrees above the western horizon. In deepening twilight, the slowly descending moon will become increasingly prominent against the darkening sky. This week’s chart is drawn for 11pm tonight when the moon will be just seven degrees above the horizon. By then it will be dark enough to see the darker part of the moon illuminated by earthshine. Sometimes called Da Vinci’s ghost, earthshine sunlight is reflected by both earth and moon before it hits our eyes.

While the lunar crescent is certainly svelte, you should still be able to see some details on its surface, especially if you use binoculars or a telescope. Look out for the dark and circular Mare Crisium (sea of crises) which will be emerging into sunlight in the northern part of the moon. If you use a telescope it is also easy to spot features on the part of the moon illuminated by earthshine.

Another thing you can look out for if you have a telescope is the reappearance of a triangle of bright stars from behind the moon over the course of the night as the moon moves along its orbit.

The moon is in the constellation Sagittarius and tonight is situated among the triangle of stars that some astronomers think resembles the lid of a teapot. Because the majority of our constellations were named by northern hemisphere astronomers, for observers in this part of the world, the teapot is upside down.

According to legend, Sagittarius is a celestial centaur whose body is a horse but whose torso is human. The centaur, who is also an expert archer, is aiming a bow in the direction of the neighbouring constellation of Scorpius. The word "kaus" is derived from an Arabic word meaning bow, with Kaus Australis, Kaus Media and Kaus Borealis delineating its southern, middle and northern extremities.

 

- Ian Griffin