RISING MOON
The mountain above the pole
WHERE’S THE BEST PLACE on the Moon for a solar power station? That would be a massive hill on the lunar farside, just beyond the south pole, which suffers only a brief interruption in continuous sunlight. M5, unofficially known as Mount Clementine, undergoes a short eclipse as the shifting shadow of its neighbor M4 swings across it once a month. By contrast, most places on the Moon must endure the day-night cycle that sports 14 Earth nights of darkness.
Without a doubt, Mount Clementine is the easiest farside feature to see — when the time is right. As the Moon hits a high above the Earth-Sun plane (the ecliptic), depicted as a red line on our Star Dome (see page 34), we have the opportunity to peer a bit beneath its south pole. Start on the 14th and return nightly through Full Moon on the 16th, when we get a near-perfect, outstanding 3D perspective.
It’s as if you were in a helicopter flying low over waves rushing toward a beach. Our extra viewing angle shows us the shadow cast by every hill, reminiscent of the way dark eyeliner highlights the white of the eye.
Instead of shadows lying west of a rising Sun, here they are cast southward, gradually swinging around in an arc. The modestly tall bump in front of Mount Clementine at first casts its shadow to all the way to the base of M4; on following nights it marches eastward, crossing the base of Clementine. A few nights later, M4 itself puts Clementine in darkness, as in the image here. Use Casatus, Moretus, and Newton to nail the identification.
Be patient and wait for good seeing. The views will be quite rewarding. You may also pick out the crater rims of Shackleton and Faustini on the farside! At lower power, the glare from the Full Moon can be rather unbearable in larger instruments, so use a dark blue or green filter. But as you step up the power, you might not need one. Go back for another round next month near Full Moon, since the geometry almost repeats.