The big three

4 min read

The top sights to observe or image this month

A celebration of clair-obscur effects

Where to look to find the clair-obscur effects that are visible during January



A lunar clair-obscur effect is a trick of the light that appears as something familiar or unusual through the eyepiece. They provide interesting targets which can help you explore and familiarise yourself with the Moon’s surface.

On 4 January, Curtiss’s Cross makes an appearance. Best seen around 01:20 UT, the cross can be tricky to see, but with perserverance you’ll make out a small, illuminated 50km Maltese Cross formed by sunset highlighting peaks immediately northeast of 96km Fra Mauro.

Also in the early hours of 4 January, Gruithuisen’s Lunar City makes an

appearance. Despite its grandiose name, this can be hard to see because of its subtle nature. It occurs when the evening terminator sits east of the region near 35km Schröter. A herringbone shadow pattern appears north of 9.5km Schröter A which sits immediately north of Schröter. The pattern was once thought to be the streets of a city named Wallwerk, evidence for inhabitants on the Moon. The ‘city’ is optimally visible around 05:20 UT.

Visible on the evening of 18 January is the Face in Albategnius, formed when the shadows of Albategnius’s eastern rim fall on the crater’s floor, forming the silhouetted profile of a face. That evening there’s also a chance to see Nessie within 154km Ptolemaeus. A protruding shadow across the crater’s floor appears similar to the famously faked ‘Surgeon’s photo’ of the Loch Ness Monster, the one showing the monster’s neck and head in silhouette against the loch’s waters. Nessie is best seen through smaller instruments.

On 19 January there are three effects to look out for. Just into the morning at 00:04 UT, look at 55km Aristillus where you will see the many peaks of its central mountain complex illuminated to appear like a small cluster of stars: the Stars of Aristillus. In the afternoon, catch a view of 225km Clavius around 15:50 UT and you should see two illuminated crater rims on its dark shadowed floor: the Eyes of Clavius. Later that evening, 101km Plato has a rim peak shadow passing over its floor. This can appear curved and is known as Plato’s Hook.

In the early hours of 21 January, the impressive illuminated arc of the Jura Mountain range can be seen extending into the lunar night: the Jewelled Handle. Finally, in the early hours of

This article is from...

Related Articles

Related Articles