The skies belong to everyone, part one: The Moon

Posted by David Eicher
on Monday, May 2, 2011

So, you bought a telescope to look at everything the universe has to offer. There are moons, planets, stars, comets, nebulae, and galaxies, many of which are visible to users of small telescopes on any clear night. What should you look at first?

Photo credit: Lee Decovnick
There’s no better way to start in astronomy than with the Moon. The brightest and largest object in the sky, the Moon is covered with features easily visible in binoculars or small telescopes. You can actually see some lunar features with your unaided eye, most notably the dark lunar lowlands — vast plains of congealed lava — called maria (from mare, Latin for sea). Indeed, the “Man in the Moon” comes from several large maria that form a dark “face.” The most striking patches of darkness visible against the Moon’s brilliant surface are Oceanus Procellarum, Maria Inbrium, and Nubium on the western side, and Maria Serenitatis, Tranquillitatis, Nectaris, Fecunditatis, and Crisium on the eastern side.

To see anything of the Moon beyond its great “seas,” however, your eyes need help. Binoculars show the maria in better detail along with a few prominent craters. Better still, a small telescope working at about 60x makes the Moon come alive with features: the craters Plato and Copernicus straddle Mare Imbrium, itself partially encircled by a broken chain of mountains called the Apennines; the pockmarked central highlands feature densely concentrated craters scattered pell-mell; and Mare Nubium hides the “Straight Wall,” a gigantic cliff visible only when illuminated from the right angle.

There is an enormous amount to see on the Moon — a few nights spent observing it will surely convince you of that. Try watching over successive evenings and observe how features change as the Sun journeys slowly through the stark lunar sky — its rays passing across craters, hills, and valleys. At sunrise, shadows are long and black — every little detail stands out clearly. Then, as the Sun climbs higher, shadows shorten and the terrain appears to flatten. At Full Moon, craters disappear in the hot glare of noon. As the phase shifts toward Last Quarter, the evening terminator — the line between night and day — crawls westward, painting the rugged topography with shadows once more.

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