Using the Moon Map

To use the accompanying map, turn it around until it matches the view in your binoculars. Start your tour by learning the Moon's large, dark plains, called maria (the Latin plural of mare, "sea"). Early telescope users and mapmakers in the 17th century thought these dark markings were similar to Earth's bodies of water and gave them fanciful names like Mare Nectaris, "Sea of Nectar," and Mare Nubium, "Sea of Clouds." Today we know that the Moon is an airless, waterless, and lifeless world. The maria are in fact great lava flows that filled much of the lunar lowlands billions of years ago.

When the Moon is a slender crescent in the western sky after dusk, we see the features near the right-hand edge of the map. As you can see, Mare Crisium and Mare Fecunditatis are the only major "seas" visible. In the next few days the retreating terminator gradually unveils Mare Nectaris, Mare Tranquillitatis, and Mare Serenitatis. At first-quarter phase we see the entire right half of the map. After first quarter Mare Imbrium and Mare Nubium appear, and just before full, Oceanus Procellarum and Mare Humorum come into view.

At full phase the Moon is at its dazzling brightest. Because the Sun shines onto the Moon from almost directly behind us at this time, we see no shadows of craters and mountains. The bright ray system of the craters Tycho, Copernicus, and Kepler stand out especially prominently. The rays are splash patterns of debris from the impacts that formed the craters. After full phase the advancing terminator covers up the surface in the same right-to-left order.

Unlike astronomical telescopes, which give inverted (upside-down) and sometimes mirror-reversed images, binoculars show you right-side-up views that are never mirror-reversed, making comparison with the lunar map very easy. Once the map is oriented properly, you will be able to readily identify the major seas, craters, mountain ranges, and other features. In time the geography of this alien world will become as familiar to you as that of our own.