Can you spot Crater Einstein, a lunar feature barely visible from Earth?
Crater Einstein is a large feature near the Moon’s western limb, but can only be seen from Earth during favourable conditions.
Being 171km across you’d think Crater Einstein would be easy to see, but it’s not, mainly because it’s so close to the Moon’s western edge, in the libration zone.
Over time, the Moon rocks and rolls slightly as seen from Earth, an effect caused by its elliptical and tilted orbit.
This is known as lunar libration, and perhaps the most famous example of a feature only visible during libration is Mare Orientale.
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To see libration zone features, the rock and roll has to favourably tilt them into view.
Ideally, the terminator should be nearby too, as this creates the shadow relief needed to pick out structure.
Between 3 and 8 February, libration favours a view of Crater Einstein, but the Moon’s phase and altitude aren’t ideal.
That said, views of this huge crater are so fleeting that it’s definitely worth having a go.
How to find Crater Einstein on the Moon
If it’s clear on 3–6 February, first locate 40km crater Aristarchus, the brightest feature on the Earth-facing side of the Moon, and easy to identify against the dark lava of Oceanus Procellarum.
Head west from Aristarchus to locate 43km Seleucus.
Keep going past the southern tip of lava-filled 134km Eddington, nudging slightly south as you approach the limb.
This is Einstein territory, the crater best identified by the presence of 50km Einstein A located centrally inside Einstein.
Have you managed to see Crater Einstein on the Moon, or even capture an image of it? Let us know by emailing contactus@skyatnightmagazine.com.