Looking Up: Moon’s recession is short-lived

Peter Becker

It’s not just the national economy -- the moon also goes through recession after full phase and gets down to its last quarter. (Full moon arrives Tuesday, March 10, followed by last-quarter moon on March 18.)

Fortunately we can find in the lunar cycle a symbol of hope. Although the moon will be getting thinner each night, its slimming morning crescent fading to nothing as it eventually reaches new moon, recession comes to an end. The moon then resumes growing, and we see the Man in the Moon’s cheery face in full once again.

A first close inspection of the moon through even a small telescope has sparked a lifetime passion for the night sky for many people. It is one thing to see photographs of the moon and quite another to look up at the familiar moon in the sky and see it magnified in full detail.

November 2009 will mark the 400th anniversary of the first observation Galileo Galilei made of the moon with his improved telescope. The Italian astronomer is regarded as the first person to turn a telescope to the night sky and bring his observations to public attention, marking a new epoch in scientific understanding.

Galileo’s work challenged the widely held belief that Earth was the center of the universe and the only imperfect world. It took thousands of years for students of the natural world to unravel what appeared to the senses to be true, from how the solar system actually exists. We are seeing everything from our lowly perspective; at first glance the world seems flat, and the sun, moon, planets and stars seem to go around us.

Incredibly dedicated and intense observation of planetary motions and location of stars was done even before the invention of the telescope. Those observations, as well as the revolutionary insights revealed at the eyepiece, created no less than a revolution in our view of the cosmos.

Galileo’s astonishing view of the rugged lunar surface shattered the concept that the moon was a perfect orb, raising questions of the nature of things. His 20 power telescope showed the moon to be covered with dark plains, bright regions, craters of all sizes, some with rays streaked across the moon, and mountain ranges.

All you need is a pair of binoculars magnifying 7x or 10x to start to show the moon’s battle-scarred surface. You will find it best to position your binoculars against a steady support.

As the moon progresses night to night toward full phase, you will see how the changing angle of sunlight fills in a new line of craters and mountains. The dividing line between the sunlit moon and the portion still dark is called the “terminator” and is the line of lunar sunrise prior to full moon and line of sunset after full moon.

The dark, smooth plains, which make up the imagined features of the Man in the Moon, are hardened lava beds. In most cases, lava erupted or flowed into large impact basins, covering up craters and mountains. With a telescope, you can see here and there peaks of mountains and ridges that peek through the lava, and “ghosts” of crater rims indicating a buried crater. At one time these plains were thought to be bodies of water, and to this day, they are referred to as “maria,” Latin for “seas.”

Interestingly, the far side of the moon is almost entirely without maria. The far side was first photographed by the Soviet Luna 3 probe in October 1959.

Until spacecrafts began close-up studies of the moon, there was a raging debate among scientists of the origin or craters. Some held to a volcanic origin rather than meteoric impacts. The large craters were formed from collision with asteroids or comets. Some struck with such force, rays of brighter material were unearthed (unmooned?) from below, and spread across the face of the moon. Tycho’s system of rays is the most easily visible. There is an estimated half-million craters with a width of about a mile.

How close can you see? Although the moon averages 238,000 miles from Earth, if you divide that number by your magnification, you can tell how close the moon appears to be. A 10x binocular view brings the moon to 23,800 miles. A small telescope might reach to 150x, allowing you to “hover” 1,586.6 miles above the moon. A 10” telescope, used by many backyard astronomers, can bring you down to about 476 miles (500x).

Moon-like landscapes are common. Mercury and Mars are riddled with craters, as well as many other moons. Earth has meteor craters, although most have been erased by erosion. Meteor Crater in Arizona is likely the best known.

Keep looking up!

Your questions, reports and comments are welcome. E-mail pbecker@wayneindependent.com.