Editor’s note: A version of this has been previously published on the author’s website.
Our only natural satellite is where many astronomers start their gazing. That first small telescope or pair of binoculars shows the moon as an astonishing place. Instead of a glare in the sky, the view through a telescope brings out a realm of craters — surprising holes and rims strewn across the white crescent. Then there are large dark blotches that, you learn, are dry stretches ironically termed seas. An entire rugged world of jagged shadows and mountain peaks appears.
The problem with Luna is its exceeding brightness; even a partial phase will wash out other celestial objects. Galaxies lose contrast or disappear altogether and nebulas’ colors are off. The searchlight above is a horrible source of light pollution.
Perhaps the majority of gazers who continue with astronomy soon decide the moon is a nuisance to be avoided. In planning excursions to dark sites, they count the days until new moon, when it will be absent from view. If delayed until shortly after those few new moon nights, they must wait for the moon to set before beginning to record or regard the dim, glorious deep-space objects they love.
Yet even for the experienced telescopist who has graduated to faint distant targets, the first glimpses at the moon may remain a touchstone moment, a time stamped into memory, to be revisited over succeeding decades. These recollections retain the feelings of surprise and appreciation, a kind of astronomical nostalgia.
With the onset of winter, this could be a good time to rediscover our moon and fall in love again with its strange beauty.
A trip to a dark locality is never required to observe and/or photographing the moon — it’s right outside, glowing into the backyard. One need not prepare the telescope after hours of driving. Instead of a night spent shivering in the desert, the astronomer can duck inside the house to warm up. Best of all, our natural satellite is brimming with dramatic vistas and fascinating geology, available to explore with modest equipment.
Wintertime observers should be aware of weather that could impact or forbid telescope work. Sometimes a specialized dew heater may be needed.
If the goal is visual astronomy, a good investment is a lunar filter, a device that fits onto the telescope eyepiece and reduces the moon’s powerful flare. Without one, the view can seem blinding, depending on lunar phase and the instrument’s light-gathering ability. One popular supplier chosen at random — OPT of Carlsbad, California, an online retailer — sells lunar filters priced from $8.96 to $84.
Guides to the moonscape will help identify craters, rills, lava plains, seas, mountain ranges and ejecta rays; the last are where debris from asteroid impacts sliced across the moon’s face. Guidebooks can be purchased at bookstores or downloaded. A fine guide available for free was placed online by the University of Arizona’s Lunar & Planetary Laboratory. Titled ”Rectified Lunar Atlas,” it presents a schematic of the near side divided into 30 zones of varying sizes. Click on any zone and labeled photos of that area pop into view.
The best times to examine the moon are when it isn’t full. Then, the terminator, the line between daylight and night, will show features in stark relief, with shadows stretching from craters and mountains. But the full moon is fascinating too.
Photographing the moon is more expensive and difficult than observing. But with the right equipment and enough effort, the rewards are high.
The better the telescope, the better the chance of a good photo. The camera can be anything from an ordinary digital single-lens reflex to a dedicated lunar and planetary model. Once attached at the proper distance and focused, a digital camera is as easy to use here as snapping a photo of the family cat. More elaborate cameras may require imaging programs and a laptop to accumulates and stack hundreds or thousands of pictures that flood in.
Mare Imbrium is the biggest impact basin on the moon’s near side and is visible to the unaided eye as the biggest dark rounded splotch on the moon’s face. It has a diameter of more than 720 miles, according to the Lunar and Planetary Institute of the Universities Space Research Association. “The Imbrium Basin is also the second youngest basin on the Moon,” the institute notes. “Based on samples returned by Apollo 15, it formed about 3.85 billion years ago.”
With bombardments of space rocks walloping the moon, underground basalt melted and lava rose into Imbrium and other regions. The Smithsonian Institution’s National Air and Space Museum informs us, “Lunar surface basalts are believed to have their origins in partially melted areas 100-400 kilometers (60-250 miles) beneath the large meteoroid impact basins. The basaltic material welled up into the basins through cracks created by the impacts. The basalt flows covered areas up to 1200 kilometers (750 miles) away from where they had arisen. …
“Nearly 26% of the near side of the Moon is basalt and only 2% of the far side is basalt. Most basalt in either hemisphere is found in areas of lowest elevation, particularly in the very large impact basins.”
According to a July 20, 2016, news release issued by Brown University of Providence, RI, the object whose impact formed Mare Imbrium was “more than 150 miles across, roughly equal to the length of New Jersey....” The university says the new size estimate, published in the journal Nature, “suggests an Imbrium impactor that was two times larger in diameter and 10 times more massive than previous estimates.
“‘We show that Imbrium was likely formed by an absolutely enormous object, large enough to be classified as a protoplanet,’ said Pete Schultz, professor of earth, environmental and planetary sciences at Brown University. ‘This is the first estimate for the Imbrium impactor’s size that is based largely on the geological features we see on the moon.’”
The moon provides fodder for endless examination, features that are visible from anywhere on Earth. Some like the Imbrium Basin are visible to the unaided eye, while other intriguing details proliferate with magnification.
Joe Bauman, a former Deseret News science reporter, writes an astronomy blog at the-nightly-news.com and is an avid amateur astronomer. His email is firstname.lastname@example.org.