The moon is a great way to begin touring the cosmos. If you have never used your telescope to get up close and personal with our nearest celestial neighbor – the next two nights offers some amazing views of a two wonders of the moon.
As the moon goes through its phases, most of the time being partially lit by our sun – topographical features cast long shadows near the terminator – or shadow line visible on its surface. Cruise along that border between lunar night and day with any sized telescope and you get to see some amazing things.
Tonight, on November 2nd around 11 pm local time, as the moon enters its quarter phase, like it does every month, a weird formation magically appears for only a four hour period- a tiny letter X formation – visible with the smallest telescope and steadily held binoculars even. Nothing artificial about it however, this conspicuous X is formed by the walls of three craters clustered together. While the crater floors are in total darkness and sunlight hits the craters rims just at the right angle, they create this optical illusion for observers. Not many have observed it because it’s only visible for a few hours each month.
Start your hunt for the lunar X about a third of the way up from the heavily cratered, southern limb of the Moon, along the terminator line. You’ll find a good finder charts with observational details in this article .
For those that want an added lunar challenge that never fails to impress – try spotting Rupes Recta, otherwise known as the Straight Wall or the Railroad. This long straight line that cuts into the otherwise smooth region of the Moon lies along the eastern shores of Mare Nubium ‘Sea of Clouds’ and is the best example of a lunar fault line.
Best visible on November 3rd just after the first quarter moon , the 110 km (68 miles) long Wall casts a striking shadow along its entire length. Located near the high southern face of the Moon, the wall ends in the south within a curved mountain group called the Stag’s horn – looking more like a sword handle, with the wall being the blade.
Various measurements puts the height of this cosmic precipice somewhere between 200 and 450 meters, (800 to 1000 feet) rising above the lunar plain at about 20 degree angle. Many astronomers have pointed out that the illusion of this steepness of the Straight Wall is because heights of objects close to the lunar shadow line are often exaggerated by the low angle rays of the sun.
You can have another chance to see the Straight Wall during last quarter Moon (Nov.18) when the setting sun illuminates the face of the long cliff, making it appear as a bright, white straight line – equally as dramatic.
One day Rupes Recta may become a destination of choice for lunar hikers, in the meantime check out this amazing computer generated flyover of the terrain around the wall, based on the fantastically detailed imagery returned by the Japanese lunar orbiter Kayuga in 2009. Hint: Make sure you watch it in high-def – it’s pretty awesome.