As familiar and innocuous as it might seem, the Moon is can be one of the most fascinating targets for amateur photographers. As our closest celestial neighbor, the Moon is a subject that is always available, and thanks to the Moon’s phases, different features of the lunar surface show themselves in remarkable detail as the month progresses. Even better, the Moon remains visible even without a telescope, and many of its features can be properly identified with the naked eye, and a pair of binoculars can unlock as much detail as a telescope.
Due to the nature of the Moon’s synchronous rotation, we are only able to see one side of the Moon from Earth, known as the Near Side of the Moon. This means that everyone has the same sight of the Moon’s features, with the caveat of slight changes depending on the Moon’s orientation depending on your area’s horizon. An example of this is how the Moon’s visage exists as a vertical mirror of itself in respect to whether you are viewing it from the Northern or Southern Hemisphere—If the Moon can be considered upright in the Northern Hemisphere, it will appear as upside down if you were to visit the Southern Hemisphere. It’s important to recognize how the Moon’s appearance is relative to your location, and for the purposes of this guide, we will be examining the Moon from the perspective of those in the Northern Hemisphere. Similarly when referencing direction on the Moon, East and West are spoken of relative to the Moon’s surface, thus reversing what we typically assign as Eastern and Western directions.
This moon observation guide will teach you the best times to view the Moon, as well as the types of features and locations that the lunar surface has to offer. By the time you’re done reading, you’ll be able to see the Moon in a new light, and hopefully, will harbor a greater appreciation for the Earth’s orbital partner.
Lunar Phases
The lunar cycle occurs in eight distinct phases, and the full cycle takes roughly twenty-nine and a half days to complete. Because the lunar cycle does not align perfectly to our calendar month, the dates for each of these phases change month to month and year to year. A lunar cycle always begins with what is known as the New Moon, occurring when the Moon is positioned between the Earth and the Sun, which caused the Moons to darken in its intensity, appearing near invisible. After this comes the comes the Waxing Crescent, as the right side of the Moon slowly becomes more and more visible, until it hits the third phase, known as the First Quarter Phase.
A First Quarter Moon sees the right half of the Near Side of the Moon fully illuminated, with the dividing shadow known as the Lunar Terminator. The Moon’s Quarter Phases are the best time to view the Moon, as the Lunar Terminator casts long shadows on the features of the lunar landscape, drawing out physical contrast.
From here, the wave of illumination continues to move across the moon into the Waxing Gibbous Phase, where only a small crescent of the Moon’s left side remains covered in shadow. As this darkened crescent fades, the mid-point of the Moon’s cycle occurs with the Full Moon, the Moon’s fifth phase. The Full Moon can be a fantastic time to view the Moon, particularly when looking for craters and their ejections. After the Full Moon, the Lunar Terminator moves from the right side of the Moon to the left, opposite of the first half of the cycle, creating the Moon’s sixth phase, the Waning Gibbous, when the shadowed part of the moon creates a darkened crescent on the Moon’s right side. The Terminator will then continue to move across the right side of the Moon until it reaches the halfway point with the seventh phase, the Last Quarter Phase. Finally, the Waning Crescent Phase completes the cycle as the Terminator envelopes the Moon to begin the cycle anew with the New Moon.
Selenography and Lunar Features
Although images of the Moon have been found dating back to the third millennia BCE, it was Leonardo DaVinci that first began to map the Moon in the 1500’s, labelling and demarking regions visible to the naked eye. This work that was continued by Michiel Florent van Langren and Johannes Hevelius, who, with the advantage of the invention of the telescope began to map the moon in greater detail in the 1640’s, naming specific features after canonical scholars. In 1647, Hevelius would produce the first true atlas of the Moon, named the Selenographia. This merging of lunar study and cartography is known as Selenography, and is the same process that can be recreated from your own backyard, as you begin to study the Moon on your own, recording your findings in your Observational Log.
There a number of different features of the Moon’s topography that are easily recognizable. Below is a list of these lunar features, and explanation of what they are, as well as how to find the most easily representative of their members.
Lunar Maria
Named after the Latin word for sea, Lunar Maria are the broad, dark, areas of the Moon that happen make up what is commonly described as the “man on the Moon”, or the moon’s face. Originally thought to be large oceans, the Lunar Maria are actually flat basaltic plains that are the result of ancient volcanic activity. Most of the Lunar Maria are located on the left half of the Moon, and are prominently visable during the Last Quarter Phase. There are three gauges of Maria, related to the size of the basaltic plains: Oceanus, the largest of the Maria and of which there is only one, the Maria themselves, which are mid-sized lunar plains, and the most common, and the smaller Lacus, rooted in the Latinate for lake. Below are some of the most easily recognizable Lunar Maria:
- Oceanus Procellarum (18.4°N 57.4°W): Also known as the Ocean of Storms, Oceanus Procellarum is the most easily identifiable feature of the Moon, and is the largest of the Lunar Maria. It envelopes much of the left side of the Moon, considered the Western half of the Moon relative to the surface, stretching for over 1.5 Million square miles and comprising ten and a half percent of the Moon’s surface. While we can see a large portion of Oceanus Procellarum on the Near Side of the Moon, it stretches along the side of the visible lunar surface to the Far Side of the Moon. It is speculated that Oceanus Procellarum might be resultant from an impact early in the Moon’s history, when it would have been host to seas of magma, potentially making the Maria the fourth largest crater in the solar system.
- Mare Imbrium (32.8°N 15.6°W): Also known as the Sea of Rains or the Sea of Showers, Mare Imbrium is the second largest of the Lunar Maria, and makes up the right eye of the man on the Moon. Mare Imbrium is located to the right of Oceanus Procellarum, slightly to the right of the Moon’s vertical center, and is probably the second most easily recognizable mare. The mare was also the location for the manned Apollo 15 mission, which saw the use of the first of NASA’s lunar rover.
- Mare Tranquillitatis (8.5°N 31.4°E): Also known as the Sea of Tranquility, Mare Tranquillitatis rests to the right of Mare Serenitatis, which itself sits touching Mare Imbrium to the right of the Moon’s vertical center, making both Mare Serenitatis and Mare Tranquillitatis visible during the Moon’s First Quarter Phase. Mare Tranquillitatis is known its bluish tint, which is exacerbated in comparison to the rest of the Lunar Maria. It was also the location of the infamous Apollo 11 landing, which saw the first manned mission to the Moon, carrying Buzz Aldrin and Neil Armstrong to make their one giant leap for mankind.
- Lacus Veris (16.5°S 86.1°W): A smaller Mare, Lacus Veris is also known as the Lake of Spring and rests in the center of the larger Mare Orientale. Lucas Veris has an arched crescent shape that provides for fascinating visuals, as it is filled with eleven different Lunar Rilles, another feature of the Lunar Surface we will soon cover, along with a number of long extinct shield volcanos. In 1989, a site nearby to Lacus Veris was proposed as a potential building site for a future moon base.
Lunar Rilles
Lunar Rilles are long, stream-like depressions that cover the surface of the Moon. They are most common within Lunar Maria, and because of this it is speculated that Rilles are channels denoting remnant lava tubes that have long since collapsed. There are three main types of Lunar Rilles—First there are Sinuous Rilles, which usually begin at the edge of extinct volcanos and take the shape of an established river path, forking and winding as they lead through the Maria. Then there are Arcuate Rilles, which are found on the outer edges of the Lunar Maria, and tend toward a smooth curved contour. Finally there are Straight Rilles, which take the shape of long straight paths and typically cross through craters and mountain ranges, leading astronomers to believe that they are sections of the lunar surface that have sunk between two faults running parallel to one another, a geologic phenomenon called a graben. When given names, Rilles are referred to as Rimae when they consist of a singular Rille, and Rima when they consist of multiple Rilles.
- Rima Hadley (25.0°N 3.0°E): Running a span of fifty miles along the Apennine Mountain Range, Rima Hadley is a Sinuous Rille that holds the honor of being the only Lunar Rille that has been visited by humans, which occurred during the course of the Apollo 15 mission at Mare Imbrium, in which Rima Hadley resides. It has an average width of three-fourths of a mile, and its depths range from six-hundred feet to twelve-hundred feet deep near the Apollo 15 landing site. Rima Hadley begins in an area spotted with geologic domes, raised circular mounds of lunar terrain, possibly formed by an impact event, as well as Crater Béla, which is believed to have functioned as a volcanic vent.
- Rimae Sulpicius Gallus (21.0°N 10.0°E): Bordering the Sulpicius Gallus Crater at the southwest edge of Mare Serenitatis, this chain of Rilles stretching for fifty-six miles are a prime example of Arcuate Rilles.
- Rima Ariadaeus (6.4°N 14.0°E): A massive Straight Rille that stretches for over one-hundred and eighty-six miles, Rima Ariadaeus is named after the crater Ariadaeus that rests at the Rille’s east end. It is located in the highlands between Mare Vaporum and Mare Tranquillitatis, and runs between the Silberschlag Crater and the Julius Caesar Crater.
Lunar Dorsum
Also known as wrinkle ridges, Lunar Dorsum are vein-like ridges that run along the surface of Lunar Maria. They are formed by the cooling and contracting of basaltic lava flows that initially formed the Maria. Lunar Dorsum are commonly seen forming a circular pattern that outlines the Maria, as well as forming concentric circles around impact sites, the latter providing evidence for constant variation and shifting of the lunar surface.
- Dorsum Buckland (20.4°N 12.8°E): A large Lunar Dorsum that stretches for two-hundred and thirty-six miles, Dorsum Buckland is one of the largest Lunar Dorsum in diameter. It is located within Mare Serenitatis, and is named after William Buckland, a British geologist who lived in the nineteenth century.
- Dorsa Tetyaev (19.9°N 64.2°E): Laying at the edge of Mare Crisium, Dorsa Tetyaev stretches for one-hundred and seventeen miles. It is located nearby the complex Eimmart impact zone, a series of nine craters positioned between Mare Crisium and Mare Anguis. Dorsa Tetyaev was named after soviet tectonic geologist Mikhail Tetyaev who lived in the early to mid-twentieth century.
- Dorsum Oppel (18.7°N 52.6°E): Surrounded by a number of craters, including the Yerkes Crater to the south, the Picard Crater to the southeast, the Peirce and Swift Craters to the northeast, and the Tisserand Craters to the northwest, Dorsum Oppel offers quite the selection in its vicinity. It rests in the west of Mare Crisium, and stretches for one-hundred and eighty-five miles, running north from the Yerkes Crater. Dorsum Oppel is named after Albert Oppel who was a German paleontologist who lived in the nineteenth century.
Lunar Craters and Catenae
There are two types of craters, namely impact craters and volcanic craters. Because the Moon’s volcanic activity and atmosphere are long extinct, all of the craters on the Moon are impact craters caused by colliding asteroids and meteoric activity. While the Near Side of the Moon might look overly pocked to us, it is nothing compared to the Far Side of the Moon, which is nearly entirely covered with craters. There are so many craters, in fact, that crater names make up ninety-five percent of all lunar designations.
There are a number of crater specific features to be observed on the Moon, such as a Terraced Crater Walls, which occurs when an impact pushes the lunar soil to the outter edge of an impact, creating a high rising wall surrounding the crater. There are also Central Peaks, which occurs when debris from an impact settles to form peaks in the crater’s center. Often times, the ejected material doesn’t settle in the center of a crater, and is flung far from the crater creating what are called Lunar Rays, or long trails of debris ejected from an impact site. These are best seen during a Full Moon. When a series of craters are chained together, they are called a Catanae, of which there are many on the Moon.
- Tycho Crater (43.31°S 11.36°W): Located on the southern lunar highlands, the Tycho Crater is quite possibly the most prominent of all the Lunar Craters. Estimated to have been formed by an impact 108 Million years ago, it is a relatively young crater by lunar standards. The crater’s Lunar Ray’s stretch as long as nine-hundred and thirty-two miles, and the crater itself has a diameter of fifty-three miles, with a depth of just under three miles. The Tycho Crater is so large that it is easily recognizable to the naked eye, partially thanks to the high levels of albedo, or high contrast reflective material. The impact site is also pocked with a number of smaller craters.
- Reiner Crater (7.0°N 54.9°W): Located in the vast expanse of the Oceanus Procellarum, the Reiner Crater has a number of unique features that make for worthy viewing. The Terraced Walls of the crater are especially well defined, and the center of the crater features a Central Peak as well. Surrounding the Reiner Crater are a number of satellite craters, but located slightly to the north west of the Reiner Crater is a Lunar Swirl called Reiner Gamma (7.5°N 59.0°W). Lunar Swirls are a somewhat rare lunar feature characterized by high albedo and high magnetic activity in relation to the rest of the Moon. Reiner Gamma is characterized by its oval shape, which many viewers liken to a fish, as well as its distinct swirling and loop-like patterns.
- Catena Davy (11.8°S 8.1°W): Created by a single mass that broke up upon impact, Catena Davy is a visually fascinating chain of twenty-three impacts that rests on the eastern edge of Mare Nubium. Davy itself features a crater that overlays an older crater known as Davy Y, led up to by the long curved impact chain, known as a Catena.
Mountains and Mountain Ranges
Just like the Earth, the Moon is home to a number of mountains and mountain ranges. Although the tallest peak on the Moon is located on the Far Side of the Moon, known as the Selenean Summit and standing twenty-percent higher than Mount Everest, the Near Side of the Moon offers many mountain ranges to gaze upon.
- Mons Huygens (19.92°N 2.86°W): Reaching three and a half miles at its tallest point, Mons Huygens is the tallest mountain on the Near Side of the Moon. Mons Huygens is located on the Montes Apenninus mountain range, which was formed by the same impact that created Mare Imbrium. Nearby the Mons Huygens are the craters Huxley, Wallace, and Huygens.
- Mons Hadley (26.69°N 4.12°E): Featured in the background of many Apollo 15 pictures, Mons Hadley sits in the northern part of the Montes Apenninus range, and stands at just over two and a half miles. Nearby is the smaller peak of Mons Hadley Delta, which stands at just over two miles and was explored and sampled by the crew of Apollo 15. Rima Hadley also runs nearby.
- Montes Haemus (19.9°N 9.2°E): Rising one and a half miles, Monyes Haemus is a lunar mountain range that rests on the edge of Mare Serenitatis and straddles craters Sulpicius Gallus, Auwers, Manilius, Menelaus and Plinius, until the range comes to an end near the convergence of Mare Tranquillitatis and Mare Serenitatis. A series of Lacus also reside on the edge of the Montes Haemus, which are Lacus Odii, Lacus Doloris, Lacus Gaudii, and Lacus Hiemalis. There are also a number of Rilles that run the ranges eastern edge, most notably Rimae Sulpicius Gallus, Rimae Plinius and Rimae Menelaus.
Lunar Valleys
Similar in nature to Lunar Rilles, the Lunar Valleys are deep depressions that cut into the lunar surface. These valleys can stretch for hundreds of miles, although they are typically only a mile or so wide, and are often intersected with Lunar Rays and impact craters. The majority of Lunar Valleys exist on the Far Side of the Moon, although there are some on the Near Side. Typically, Lunar Valleys are deeper than the Lunar Rilles, however there are a number of both Rilles and Valleys that have been the subject of great debate as to which classification they should hold.
- Vallis Snellius (31.1°S 56.0°E) and Vallis Rheita (42.5°S 51.5°E): Together, these two lunar valleys form a radial path toward Mare Nectaris, which has led astronomers to believe that they share a common origin. Running for a length of three-hundred and sixty-eight miles, Vallis Snellius is the northernmost of these two lunar valleys and the longest of the lunar valleys on the Near Side of the Moon. Its path intersects the Snellius Crater for which it is named, and culminates at Crater Borda. Flanking Vallis Snellius are the craters Furnerius, Stevinus, and the Reichenbach Catena to the south, and to the north lies the Petavius Crater. Vallis Rheita runs for two-hundred and seventy-six miles, making it the second longest of the Near Side of the Moon’s lunar valleys. Vallis Rheita intersects a large number of craters, which can ultimately obscure the valley, the most notable of them being Crater Rheita, for which the valley is named, and Crater Young. To the south lie the interesting set of Craters Janessen, Fabricius, and Metius, which all overlay each other forming out of the largest and oldest of the three, the heavily worn Crater Janessen.
- Vallis Alpes (48.5°N 3.2°E): Bisecting the Montes Alpes lunar mountain range, Vallis Alpes runs for one-hundred and three miles, beginning at the basin of Mare Imbrium, and the valley has a maximum breadth of just over six miles in its middle. At the bottom of Vallis Alpes lies Rima Alpes, a long narrow Rille that is notorious for the difficulty is sighting it for amateur astronomers, and exists as a sort of Holy Grail for many. It is speculated the Vallis Alpes might either be an enormous graben that was later filled with magma from Mare Imbrium and Mare Frigoris, or a giant stress fracture in the Moon’s mantle.
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