For the owner of a small telescope, the moon is more interesting than anything else in the sky, because it is close enough to see really well. Even binoculars will show features on the surface. But you do not need a telescope to enjoy the moon. Even a casual glance at it on a nightly basis reveals its path through the constellations of the constellations, their relentless progress of phases, frequent encounters with bright stars and planets, as well as accidental eclipses and unusual atmospheric effects.
On Thursday evening (August 20), very low in the western sky, two days a slender swing of a Crescent Moon was past new phase. This was a celestial signal through which the ancestors set their calendars. Astronomers have mapped the face of the moon by looking at it over a period of time as it grows from new to full and from full to old.
In the long morning of the moon (the moon takes 27.3 Earth days to rotate once), his face is illuminated from the right side. The line of sunrise slowly moves across his face. Mountains climb out of the night as their peaks capture the first rays of sunlight. By noon the moon is full and the mountains are difficult to see. When the sun begins to set in the afternoon of the moon, the moon is illuminated again, this time from the left, and its mountains cast black shadows.
Related: How to observe the moon (infographic)
The face of the moon, slowly revealed
The moon was new and effective from our point of view on Tuesday (August 18). Evening (August 21), about 45 minutes after sunset, you can catch a glimpse of a beautiful thin moon dog, moving just above the horizon, just south of the right west.
As the moon ascends the western sky this week, look at it with binoculars, which will greatly enhance the view of the phenomenon known as “Earthshine” – the rising crescent moon appears as a thin arc of yellowish-white light enclosing a ghostly blue-gray ball.
Indeed, for at least several nights, until almost a week after the new moon, sunlight from the Earth illuminates the night side of the moon, making its entire disk visible. Here is one of nature’s most beautiful sights, and IT fits in with the old adage: “the old moon in the arms of the new moon.”
Lunar functions were called, sometimes fancy, by astronomers who began with the Italian astronomer Giovanni Battista Riccioli in 1651. Dark, smooth areas were thought to be water functions, and so were called (merje in Latin). Mountains were often named for earthly reach. Craters were named for prominent early philosophers and scientists. A crater you have mentioned is a mixed blessing: it is a great honor, but you should normally be dead.
On Thursday (August 20), Mare Crisium, the Sea of Crises, enjoyed sunshine. On Friday the sun shines on Mare Fecunditatis, the Sea of Fertility. Then on Saturday the sun rises on Mare Nectaris, and Thursday (August 27) is the morning session for Mare Tranquillitatis, the Sea of Rest, landing site of the historic Apollo 11 mission.
The best time to view the moon
The month will continue through Tuesday (August 25) through the first quarter phase at 1:38 PM EDT (1738 GMT). At that point, the moon will appear just 50% lit; its right or west side will be illuminated, while its left or east side will still be in darkness.
If the sky gets dark enough that evening, a close examination will reveal that our natural satellite is no longer in a “half moon” phase. Because then the moon will actually be slightly more than half lit – 53% to 54% to be exact; so actually it will be a growing gibbous phase. That evening look to the bottom left of the moon and you will see the bright reddish star Antares marking the heart of the scorpion of the constellation of Scorpius.
We would of course assume that if half of the moon’s disk were illuminated, we would get half as much light as at full moon. Actually, we only get one-ninth as much. The reason is that a large part of the moon’s surface is covered by shadows of mountains and craters, and that therefore less than half of its disk is illuminated by the sun. The moon is a little brighter in the first quarter than in the last quarter, because some parts of the moon reflect better than others.
The light / dark border, called the terminator, is the best place to look, as the mountains cast the longest shadows in the rising sunlight. The moon has always been a primary target for telescope observers everywhere and shows great detail in even the smallest telescope. Even binoculars will see the mare as “seas”, mountain ridges and ring plains, as well as the large craters, while with a telescope of only 3-inch (8 cm) aperture you can see practically everything as clearly as the deepest Earth-based photos .
Related: How to observe the moon with a telescope
Most observers agree that the longest time to see the moon is in the interval of two or three days after the first quarter phase. The moon is then in a good position for evening study with most of its main features visible, although it is not too bright to cause a loss of detail due to glare.
In fact, the mountains can not be clearly seen when the moon is full; There are no shadows visible to create relief against the mountains. A full moon appears flat and one dimensional. Through a telescope, features near the terminator stand out in bold, broken and jagged relief; shadows are strong and details are easier to see. Sometimes you can even spot bright spots of light where high mountains capture the light of the rising sun before it reaches the plains below.
‘The monarch of the moon’
On Thursday (August 27), sunrise will hit one of the most remarkable craters to be seen on the lunar surface. This is the crater of Copernicus, nicknamed the ‘Monarch of the Moon’ by lunar cartographer Thomas Gwyn Elger. Copernicus is thought to be a crater of the lunar impact, formed by the collision from the fragment of an asteroid about 800 million years ago.
It is a circular crater that is 93 kilometers (about 3 kilometers) across and 3.8 kilometers (3.8 km) deep. There are three isolated mountain peaks that stand roughly 3,200 feet (1,200 meters) high. Surrounding Copernicus is a beam system that extends 800 km in all directions. The rays consist of radial stripes of fine ejecta that were struck during the formation of Copernicus and look somewhat like ghosts coming from the hub of a wheel.
The sun will first touch the western (right) edge of Copernicus’ edge at 8 o’clock EDT (1200 GMT). The moon will not be visible from North America at this time, but later in the afternoon if you train a pair of binoculars or a small telescope on the moon, you will easily see Copernicus to the right of the terminator. The inner part of the crater will still be in darkness, but its outer extremities will be in broad daylight. Within a few hours, even the interior will bask in sunlight and on Friday (August 28) the beam system will also be in full daylight and very noticeable.
Early telescopic observations showed how lunar mountains cast long and distinct shadows at sunset and sunset, leading early observers to believe that the lunar mountains were extremely low. And yet they are not as spectacular as one might think the geometry of the projections actually works. The radius of the moon is only about a quarter of our Earth, so the horizon falls away faster. An astronaut standing in the center of Copernicus crater would not be able to see its 12,000-meter walls just 46 km (46 km) away.
So, if you have a pair of binoculars like a small telescope, be sure to train it on Thursday night on the moon and look right past the terminator and there you will find Copernicus. You can not miss it!
Joe Rao serves as an instructor and guest lecturer at Hayden Planetarium in New York. He writes on astronomy for Natural History magazine, the Farmers’ Almanac and other publications. Follow us on Twitter @Spacedotcom and on Facebook.
