How to Observe the Moon Saturday Night

This weekend brings the first global moon-watching event inspired by those who are curious about the moon, but there are some easy tricks that skywatchers may want to remember to make the most of the lunar-gazing experience.

More than 278 moon-watching events in 40 countries are planned for the International Observe the Moon Night event on Saturday (Sept. 18), and it's not hard to see why. The ever-changing moon was one object in the celestial scene that attracted my attention skyward as a young boy, with its varying phases, times of rising and setting, and other, more subtle aspects of its visibility that I still find fun to watch.

This weekend sky map shows where to look for the moon on Saturday. With a photograph or lunar map as a guide, you can easily study the moon and identify a number of its most prominent features. 

Through binoculars or a small telescope, we can see that the moon?s surface has mountains, plains, and large hollows with ridges around them called craters.

The plains, which form the dark patches, were once thought to be oceans and seas, and were given poetic names like the Sea of Serenity and the Bay of Rainbows. These names are still used, although we now know that these dark areas are flat plains of lava and that there is no flowing liquid water on the moon. Water does exist on the moon in substantial amounts in the form of ice and its chemical components.

Binoculars are a good start

Astronomy neophytes are pleasantly surprised the first time they look at sky objects with a pair of binoculars. But in reality, most amateur and professional astronomers regard binoculars as standard viewing equipment. 

Binoculars are the ideal starter instrument because they?re so simple to use. Through them, you can see the image right side up and in front of you. The large field of view makes it easy to find what you point at. 

Yet binoculars also reveal many sights that most folks think require a telescope ? including planets and their satellites, comets, asteroids, double stars, star clusters, nebulae, galaxies and, of course, the craters, mountains and plains on the moon. The moon shows at least as much detail in binoculars as Galileo saw with his crude telescopes. [Gallery: Full Moon Fever]

The very best time to observe the moon is in the three- to four-day period after first quarter, for several reasons:

• The moon is in fine position for evening study.

• Nearly all of the major lunar features can be seen.

• The moon is not sufficiently bright to cause loss of detail through glare.

• As the line of darkness ? called the terminator ? recedes, features near the border stand out in bold relief; the shadows become stronger and details are more easily seen.

Your first glance through binoculars will reveal the so-called seas or maria (plural of mare). Using a photograph or lunar map, spend a few nights outdoors identifying various lunar landmarks, they will soon become as familiar to you as the geography of the Earth. 

It reminds me of a passage written by Leslie Peltier (1900-1980) in his autobiography, "Starlight Nights" (Sky Publishing, 1965):

"Throughout these nights of discovery and exploration of the moon one question kept recurring to my mind.  Why had I been denied all this until my school years were so nearly spent? Why had it not been made a part of the growing up of every youth? I had been taught the rivers, the seas, the mountains of every continent on earth. I knew the capitals of every state and country in the world.  And all this time, right above me, the 'geography' of a whole new world had been turning, page by nightly page, and no one had opened up the book for me." 

The view through a telescope

The mountains on the moon are easier to see through a small telescope, particularly those that lie along the terminator. There, the light comes from the side and the mountains cast long shadows, just as they would here on Earth in the early morning or late afternoon. That's why brightly lit lunar peaks stand out and the moon appears more rugged. 

When I was a teenager, I used to imagine that I was an astronaut by viewing a gibbous moon at high power through my telescope; letting it fill my entire field of view.  I'd then put the moon just outside the field of view of the eyepiece and allow it to majestically drift into view. 

To enhance the effect, I'd listen to recordings of radio communications that were made during the various Apollo missions to the moon. The effect was dramatic, especially while I viewed craters and mountains, deep in shadow, slowly glide on by. Try it for yourself.

In the nights that followed, and as the terminator moved on, the sun climbed higher in the sky over the region of the moon that I was watching and the shadows grew shorter and shorter; the lofty lunar mountains seemed to melt into the landscape and almost disappear. This is why a full moon appears flat and one-dimensional, because the sun is shining on it almost directly. 

The view Saturday night

On Saturday night, the moon will be 11 days old.  That is, it will be 11 days past new phase, four days past first quarter and 85 percent illuminated; an excellent phase and position for evening study. In binoculars or a telescope, about halfway from the center of the lunar disk to the terminator, you?ll readily see the crater Copernicus, christened the "Monarch of the Moon," by English lunar mapmaker Thomas Gwyn Elger.  Surrounding this crater is a ray system that resembles a gigantic splash pattern. 

But down near the moon?s lower limb is a crater with an even more outstanding system of rays: Tycho, one of the youngest of the major lunar craters. 

British astronomer the Rev. Thomas William Webb poetically referred to Tycho as "the metropolitan crater of the moon." Its brilliant rays extend outward like a sunflower in all directions for many hundreds of miles.  Webb claimed that it?s even visible to the naked eye at full moon, something you might like to test for yourself if you have good eyesight.

 In his book "Exploring the Moon through Binoculars" (McGraw-Hill, 1969), Ernest H. Cherrington, Jr. says that Tycho?s rays "... give the full moon the general appearance of a peeled orange, the crater marking the point where the sections meet."

Observing the region near and along the terminator will reveal a host of other fascinating lunar features. And with the unaided eye we can imagine one eye of the "man in the moon" watching us; in the nights to come, the other eye will appear, and the mouth and nose, too, as the lopsided appearance of what we call the gibbous phase fills out ultimately to become the full moon.

So keep all these things in mind when you gaze up at Saturday night's moon.  After all, it's not just for werewolves and lovers!

To see if there is an International Observe the Moon Night event near you, visit: http://observethemoonnight.org/

• Gallery: Amazing Full Moon Photos
• Video - Tricks for Observing the Moon
• Telescopes for Beginners

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.