Monday 1st to Sunday 7th November 2021
When you look at the Moon, one of the most obvious features are the dark, flat areas that early astronomers used to think were seas or oceans. Probably the most famous is Mare Tranquilitatis or the Sea of Tranquility where Apollo 11 landed back in 1969 and Neil Armstrong took his first steps.
The Moon's orbital period around us and its rotational period are the same - this means that the same side of the Moon is always facing us and the "dark side" is always pointing away from the Earth. The Moon also experiences "libration" which is best described as a small slow rocking motion, so sometimes you can see a bit further round what is normally the dark side.
Monday 1st November gives you the opportunity to try spotting the Mare Orientale or Eastern Sea, confusingly located on the western edge of the dark side. It is an impact basin, created by an asteroid hitting the Moon about 3 billion years ago. When viewed from above it resembles a bull's-eye, but you will only be able to see it almost sideways-on.
The 17%-lit Crescent Moon rises above the horizon in the east a little before 3am on 1st and to make it easier to find Mare Orientale, I have included a diagram showing its location courtesy of Wikipedia and an image of what the bull's-eye looks like from overhead, courtesy of NASA and their Lunar Orbiter 4 space probe.
Copyright Adrian Dening and Radio Ninesprings 2021
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