Getting Started with the Moon

Observing the Moon is an excellent way to get started with astronomy. You can see the Moon from any area, even the most light-polluted urban sites. It looks great in nearly any optical instrument. It is easy to find. It is the closest celestial object, and offers more to see than any other thing in the sky.

But all that detail presents a problem: How do you learn what's where? I've been doing an on-again, off-again lunar observing program for the past few years, and never managed to learn the locations of the major lunar features. Recently, I've jump-started my flagging lunar observing program, and I'm now making progress in learning the layout of the lunar surface. Here are some tips I've discovered to make the process easier.

Start with Binoculars

You might have a telescope, and just about any telescope is great for viewing the Moon. But if you have a pair of binoculars, I'd suggest using those to get started.

Why? Here's a few simple reasons:

Use a Simple Moon Map

Several of the Moon maps and atlases available are good, but you can get lost trying to find things because they show you so much detail! You need to start with the big features, and then move to the small features once you have yourself oriented with the big ones.

David North, a longtime "lunatic" from the San Jose Astronomical Association, has produced his own starter template map showing some of the basic lunar features: http://timocharis.com/astro/moonmap/ You can download and print this map, and add features to it as you observe them. Dave's original article covering this map can be found here: http://ephemeris.sjaa.net/0405/d.html

Once you have your bearings with a simple Moon map, you can graduate to a full-fledged lunar atlas. The gold standard in lunar atlases is the Atlas of the Moon by Antonin Rukl. It is available for about $40, and is absolutely a must-have if you are seriously interested in lunar observing.

Choose an observing list

A guided tour, listing all the important features you need to see, will help you get oriented fast. One good place to get started is the Astronomical League Lunar Club observing list: http://www.astroleague.org/al/obsclubs/lunar/lunar1.html. This list offers 100 features to observe, grouped according to naked eye, binoculars, and telescopic views. If you complete the list, and you are a member of an astronomy club that is affiliated with the Astronomical League, you are eligible for a certificate to validate your accomplishment.

Another list you might wish to follow is the Sky and Telescope Lunar 100 list: http://skyandtelescope.com/observing/objects/moon/article_1199_1.asp. You can also find it in the April 2004 issue of Sky and Telescope magazine. This list is organized by difficulty, higher-numbered objects being harder to find. It's also meant to teach you lunar geography, and so its selection of objects is more varied and more interesting. But it is not comprehensive if you are trying to simply learn what features are where. And the higher-numbered features are meant to challenge even experienced observers.

I recommend you follow the Astronomical League list first for learning where features are located. Then, follow the Sky and Telescope Lunar 100 to visit more interesting and obscure features and learn how the Moon came to be.

Start with the Maria

The best place to start is with the maria, the dark patches on the Moon's surface. All of the major maria are identifiable with the naked eye, and in fact are naked eye targets in the Astronomical League lunar program.

After observing the Moon on and off through the telescope for years, I still didn't have a good picture in my mind where all the major features were located. After spending one evening with binoculars, identifying all the maria and seeing where they were placed on the Moon's surface, everything fell into place.

When I read about a new crater, I can now picture its location on the Moon in relation to the maria it is closest to. This gives me a general idea where on it lies on the Moon's face, so it is easier for me to look it up in a detailed lunar atlas.

Don't start at Full Moon

Full Moon can be very pretty, but it is not the best time for observing lunar features. The lunar surface can appear dramatically different, depending on whether it is lit by low or high sun. The area near the terminator, or line separating night and day, will show the most detail. That's because lunar features near the terminator are hit by the sunlight at an oblique angle, and display dramatic shadows. At full Moon, you essentially view the face of the Moon at lunar noon. At noon, objects show very little shadow, and some craters can entirely disappear from our view here on Earth. As the terminator sweeps across the Moon's surface on successive nights, new craters come into relief, and craters from previous nights get lit by high Sun and lose detail.

The Lunar Photo of the Day website has produced an excellent photo of the Moon, specially processed from many separate images near the terminator on successive nights. The result is a synthetic "full Moon" that shows all the features in shadow relief at once, an impossibility in real life: http://www.lpod.org/archive/archive/2004/03/LPOD-2004-03-23.htm. Compare this image with an ordinary image of a nearly full Moon: http://www.lpod.org/archive/archive/2004/03/LPOD-2004-03-13.htm

Some features well worth viewing around full Moon are lunar rays. These are long streaks of material that have been ejected from craters by the impacts that created them. The high sun illuminates the rays and makes them stand out most dramatically around full Moon. The most conspicuous ray system on the lunar surface emanates from the crater Tycho, and is obvious at full Moon. Another brilliant ray system sprays forth from the crater Copernicus.

Sketch What You See

Here's an accessory for your telescope or binoculars you might not have thought of: a sketchbook and and a set of sketch pencils. Even just a plain notebook and ordinary pencils will do. Look at the Moon through your telescope and try to sketch what you see. There's so much detail in the eyepiece that you might feel it's hopeless to draw it all, but try to draw it anyway.

Your first few sketches may not be worth writing home about, but the goal here isn't to become a world-famous artist. By zeroing in your attention on the things you want to sketch, you will find yourself noticing details you would have overlooked if you had simply glanced into the eyepiece. By doing so, you gain a greater appreciation of what you see, and you improve your skills as an observer.

Once you become acquainted with the Moon, a wealth of detail will unfold, and you will find yourself discovering more and more features you never knew existed on the lunar surface. That's when the Moon becomes a truly deep object for study, no matter where you live.