I’ll give you the moon...
It’s inspired songs, controls our tides and is Earth’s nearest neighbour, but how often do you actually look up at moon? Dark, clear, frosty winter nights might be the perfect time to start.
Binoculars are a better place to start than telescopes because they are easier to handle for beginners. An ordinary pair of binoculars – available very cheaply – will do just fine initially. Astronomy at its most basic is about magnification and light-gathering power. Even a moderate form of power, like those provided by a pair of 7×50 binoculars, reveals 7 times as much information as the unaided eye can see.
The moon is a great place to start for budding astronomers. If ultimately you want to see deep-sky objects inside our own Milky Way galaxy – or even outside the galaxy – you’ll want to avoid the full moon because its brightness interferes with our view of fainter objects. So you’ll need to watch the phases of the moon carefully. But the moon itself is a terrifically interesting target in its own right, and well worth studying properly before moving on.
The best time to observe the moon is in twilight, when the glare of the moon is not so great and more detail is visible.
It’s best to start moon-gazing when the moon is just past new (waxing), and visible as a slender crescent in the western sky after sunset. At such times you’ll have a beautiful view of earthshine on the moon. This eerie glow on the moon’s darkened portion is really
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light reflected from Earth on to the moon’s surface.
Each month, as the moon goes through its regular phases, you can see the line of sunrise and sunset on the moon as it progresses across the moon’s face. This is the line between the day and night sides of the moon and is called the terminator line. The best place to study the moon from Earth is along this terminator line. The sun angle is very low in this twilight zone and this means the lunar features cast long shadows in sharp relief.
You will also see grey areas on the moon. These are called maria, so named because early astronomers thought they were seas. In fact they are now thought to have formed 3.5 billion years ago when asteroid-sized rocks hit the moon so hard that lava percolated up through cracks in the lunar crust and flooded the impact basins. These lava plains cooled and eventually formed the grey areas we see today.
The white highlands, nestled between the maria, are older and they are pockmarked by thousands of craters that have formed over millions of years. Some of the larger craters are visible through binoculars. One of them, Tycho, at the six o’clock position on the moon, emanates long swatches of white rays for hundreds of miles over the adjacent highlands. This is material kicked out during the Tycho impact 2.5 million years ago.
So this winter, why not wrap up warm, get out and gaze up at the moon. It’s well worth the effort.
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