The Origin and Appearance of the Moon

Close examination of the moon’s surface, even with the naked eye, reveals it to be very rough and irregular, Figure 5.3. Vast, roughly circular darker areas that appear relatively smooth are surrounded by lighter colored regions that are heavily cratered. These differences are the result of the fascinating sequence of events that occurred in the billions of years following the moon’s formation. So where did the moon come from, anyway? Did the moon simply form at the same time as the earth? Or was it a wandering object that was lassoed into orbit by the earth’s gravity? Was it a part of the earth that somehow became separated during the early days of formation 4 ½ billion years ago?

5.3 The heavily cratered surface of the quarter moon is revealed through this view through a telescope fitted to a DSLR (digital single-lens reflex camera). The terminator line, or the boundary between the shadowed and illuminated surface, is a wonderful area to explore through your telephoto lens. Note the dark maria surrounded by the much lighter regions of impact craters.

Results first obtained from the Apollo missions to the moon and by numerous observations thereafter have shown that the moon formed as the result of a collision between an enormous object, Theia, with the already formed earth approximately 30–120 million years after the formation of the solar system. This impact ejected a huge quantity of the nascent earth, which, when combined with remnants of Theia, provided the raw ingredients of the moon. After impact, the ejected mass of mostly liquid magma began to coalesce under its own gravity to form the spherical shape that would ultimately become the moon. Its lighter minerals floated to the outer surface of the sphere, and were the first to harden into a thin solid crust covering the still-liquid magma. The still liquid, heavier and denser minerals slowly settled into the moon’s center and continued to cool.

As the moon’s liquid interior gradually crystallized into a solid, meteors, large and small, continuously peppered both the moon and the earth. These meteors largely originated from the primordial debris remaining from the formation of the solar system. Although the majority of the meteor impacts created tortured regions of craters in the moon’s crust, a few massive meteors punctured the crust and penetrated the still-liquid core. The pressurized magma then oozed through these holes and filled the fresh craters with enormous oceans of glowing, molten rock. Imagine the view from Earth! After the magma oceans cooled and froze into maria (plural Latin for mare, or sea), we observe them today as the familiar dark regions of the moon’s surface. The dark colors of the maria arise from their different chemical makeup compared to the lighter minerals that comprise the rest of the moon’s crust. In fact, most of the Apollo missions that landed on the moon did so within maria owing to their relative flatness.

As time progressed to the present day, the frequency of meteor impacts dwindled as the primordial debris was consumed. Today, significant meteor impacts with the moon and earth are almost nonexistent (fortunately!). As a point of interest, examination of the moon’s maria through a telephoto lens or telescope reveals smaller impact craters within them, indicating that meteor impacts persisted after their formation. Some of the best targets for viewing through a telescope remain these impact craters and maria, especially along the line dividing the illuminated and shadowed regions of the moon, also known as the terminator line.

One curious phenomenon that developed as the moon cooled, and which is generally taken for granted, is that we always see the same side of the moon. Ever wonder why? In fact, this observation has sometimes led to the incorrect notion that the side of the moon facing away from us is perpetually in darkness. The reason is that as the heaviest, densest core material of the moon solidified, the relentless tug from Earth’s gravity caused it to shift and settle within the moon slightly closer to the earth and offset from the exact geometric center of the moon. Thus, we actually always see the “heavy side” of the moon as it orbits the earth; it’s as if the moon could be compared to a child’s toy that can be knocked off balance but always returns to its upright position.

The Causes and Timing of Moon Phases

Suppose we look out the window this evening around 10 pm and see the familiar sight of the moon, Figure 5.4(a). You happen to know that this particular window generally faces south. Since you’re planning an astrophotography outing, there are a few questions you might want to ask yourself. Will the moon look the same tomorrow night at the same time? If not, well, how will it change—will the shadowed part be bigger, smaller, or stay the same? Also, tomorrow night at 10 p.m., will the moon be at the same place in the sky? If not, how will its position change?

5.4 This schematic illustration shows how a waxing crescent moon (a) might appear around 10 pm through a south facing window in the Northern Hemisphere. At the same time the next night, (b), the moon will appear lower, and to the left, compared to its position the previous night (dashed circle (b)).

The answers are that tomorrow night, at 10 pm (for this particular phase of the moon, which is known as a waxing crescent moon), the illuminated part of the moon will have expanded in size, and the moon will appear slightly lower and further to the east—to your left Figure 5.4(b). How can we predict this with certainty? This chapter of the book shows you how—by describing how the moon orbits the earth and how this orbit is responsible for these and many other regular and predictable changes in the moon’s appearance.

First of all, let’s just review some background information, beginning with the fact that the light that shines from the brightly lit surface of the moon is reflected light from the sun. In contrast, the dimly illuminated “shadowed” side of the moon reflects light from the earth, termed earthshine, Figure 6.3! Second, you might recall that on any given occasion, everyone on Earth will observe the identical phase of the moon; there is no difference in moon phase between hemispheres or sides of the earth. Finally, now and forever banish the thought that the shadow on the moon is the earth’s shadow. It’s not!

5.5 There are three possible orientations to consider for viewing the system of the sun, earth, and moon: (a) A birds-eye, or 3D perspective; (b) the view from “above,” or a top view, and (c) the view from the “side,” or a side view. Notice the 5° tilt between the moon and earth’s orbital planes visible in the side view (Not to scale).

Let’s start with the model of the system of the sun, earth, and moon shown in Figure 5.5. We see that we have several choices in how we can view our system. We can view it from a birds-eye, or 3D perspective, Figure 5.5(a). We can look down on it from the top, Figure 5.5(b), or we can observe it from the side, Figure 5.5(c). It’s important to bear these different views in mind.

We will focus our attention on the top view perspective of the earth and moon system shown in Figure 5.6. This figure bears careful examination—in fact, now might be a good time to get that fresh cup of coffee, a pencil and paper; and turn off your phone’s ringer! First, notice how the North Pole is visible near the earth’s center. The perimeter of the earth, as seen in Figure 5.6, contains the equator. Also, note that from this perspective, the earth rotates daily about its axis in a counterclockwise direction, and it revolves around the sun also in a counterclockwise direction. I’ve drawn in the moon in a few locations within its orbit and from this perspective it, too, revolves around the earth in a counterclockwise manner; and rotates about its own axis in a counterclockwise direction.

Observe how the halves of the earth and moon facing away from the sun are naturally shadowed; as we peer down on the North Pole, we see that half the Northern Hemisphere experiences some form of daytime, or the left side of Earth, Figure 5.6, while the other half is in shadow and thus experiencing night, or the right side of Earth, Figure 5.6.¹ So for people at different locations on Earth, they are experiencing different times of day; while folks in Los Angeles are enjoying their evening, their friends in Tehran are enjoying early morning, while those in Tokyo are enjoying mid-afternoon.

Next, recall that it takes the moon a synodic month, or approximately 29 ½ days, to travel in a complete circle around, or to orbit, the earth relative to a fixed position on Earth.² Consequently, between any two successive nights on Earth, the moon only travels a small portion (one-twenty-ninth to be exact) of its way around the Earth. This is a very important point: that during a given night on Earth, the moon remains essentially glued to its starry background and moves through the night sky effectively at the same rate as its companions. In turn, the slow rate of orbital movement of the moon coupled with the length of the day on Earth are the reasons that moonrise and moonset occur an hour later on successive nights;³ as well as the shift in position of the moon between successive nights at the same time, Figure 5.4.

Now it’s time to get down to the business of fully understanding why we observe the different phases of the moon. To do so means we need to include the side view model, Figure 5.5(c), since our view of the moon is from this perspective. Let’s break this down further with the help of Figure 5.7 (overleaf), where I’ve created a series of images simultaneously showing both top and side views of the moon at key stages of its orbit to help you understand how the moon’s appearance to us changes as it orbits the earth. I’ve placed myself in Earth’s position and orientation to emphasize our perspective of the moon in this top view illustration.

We will begin our monthly cycle with the new moon—the period of the moon’s orbit when it lies exactly between the earth and the sun, Figure 5.7(a). Observe how the part of the moon facing the sun is fully illuminated as seen from above, yet the part facing Earth is in complete shadow, as viewed from Earth from the side. Being able to understand these differences in appearance of the moon between top and side views is your key to unlocking your understanding of the causes of the phases of the moon.

Observe how several days later, the moon has orbited to the position shown in Figure 5.7(b). The side of the moon facing the sun always remains fully illuminated as seen in the top view, but as we view the moon from Earth, we now see a crescent moon—i.e. we can now see the extreme right hand side of its illuminated face, as shown in Figure 5.7(b). Several days later, or a full week from the day of the new moon, the moon has orbited to the position shown in Figure 5.7(c). Again, the side of the moon facing the sun stays fully illuminated as viewed from the top, yet as viewed from the side, as from Earth, more of the illuminated side of the moon now has swung into view, so that it appears half in shadow and half illuminated. We call this phase of the moon the first quarter, since the moon has traveled a quarter of its orbit around the earth. Furthermore, the fact that the moon takes 7 days to travel one-quarter of its orbit is the source of the week, and since it takes nearly four weeks for the moon to complete its orbit, we have the month.

Continuing on a week later, the moon has orbited to the position shown in Figure 5.7(e); we will examine the intervening positions shown in Figure 5.7(d), (f) and (h) shortly. Now the moon

5.6 This top view of the earth and moon has a lot of information that you will find useful. The moon is shown where it would be about every 3 ½ days; or every one-half week during its month-long orbit. The sun is outside the field of view to the far left. Observe the shadows on both the earth and the moon. Notice the orbital path and direction of the (a) moon and (b) Earth, as well as their rotational directions about their axes (c) and (d). Note the different times experienced on Earth for people in the different marked locations. Finally, notice the distance the moon travels in a single day, as shown between Days 14 and 15, (e), compared to the distance it travels over the course of a week, as shown between Days 7 and 14, (f) (Not to scale).

5.7 This diagram shows how the moon appears both viewed from above, or the top view, Figure 5.5(b), as well as from Earth, or the side view, Figure 5.5(c), during each of its eight main phases: (a) new; (b) waxing crescent; (c) first quarter; (d) waxing gibbous; (e) full; (f) waning gibbous; (g) third quarter and (h) waning crescent. I have placed myself in the position of the earth to show you how the moon looks to observers on Earth from this perspective. Notice how the moon appears to change phase when viewed from Earth, despite always remaining half-illuminated when viewed from above (Not to scale).

appears completely full—in other words, we are looking directly at the fully illuminated side of the moon since the earth lies exactly between the moon and the sun. Finally, one week later finds the moon in the position shown in Figure 5.7(g), where, once again, the side of the moon facing the sun is fully illuminated (top view), yet the side facing Earth (side view) again appears half in shadow and half illuminated. This phase is designated the third quarter. Summarizing these observations, therefore, we can conclude that whenever we see the moon, day or night, the degree of illumination/shadow that we observe on its surface, or its phase, simply depends on our perspective of the moon in its position relative to the sun on that particular day or night. The phases of the moon simply result from the combination of its natural shadowing coupled with our changing perspective of it each day or night as it orbits the earth.

Like Galileo, you can easily observe by yourself how moon phases occur on the next sunny day—just go outside, make a fist, hold it up in the air and see how the side of your fist facing away from the sun is naturally shadowed. If you slowly turn in a circle during a “month,” you can see how the “phase” of the shadowed part of your fist changes. When Galileo observed a similar shadow on Venus in 1610, and how it changed over time as Venus orbited the sun, he correctly deduced that Venus was not in orbit around the earth and the heliocentric model of the solar system was born!

Let’s now formally define the different phases of the moon. A moon with more than 50 percent visible surface illumination is called a gibbous moon; with less than 50 percent visible illumination, it’s a crescent moon. With precisely 50 percent visible illumination, it’s a quarter moon. With 0 percent illumination, it’s a new moon; at 100 percent illumination, we have a full moon. Furthermore, when the amount of visible surface illumination is increasing from night to night, we say the phase of the moon is waxing; when the amount of visible illumination is decreasing from night to night, we say the phase of the moon waning. Consequently, beginning with a new moon, then, we have the following phases: i) new, Figure 5.7(a); ii) waxing crescent, Figure 5.7(b); iii) first quarter, Figure 5.7(c); iv) waxing gibbous, Figure 5.7(d); v) full, Figure 5.7(e); vi) waning gibbous, Figure 5.7(f); vii) third quarter, Figure 5.7(g), and viii) waning crescent, Figure 5.7(h).

Now that you know why the phases of the moon occur, and their names, it’s time for you to learn when each phase is visible above the horizon. Recall that our view of the moon undergoes a full cycle of phases every 29 days or so, leading to the sequence of daily changes over the course of a month illustrated by the calendar for July 2019, in Figure 5.8(a). Calendars like these are available online and via apps,⁴ and easily enable you to determine the phase of the moon for any date, past, present, or future. In fact, consulting such moon phase calendar tools will soon become one of your very first steps in planning your astrophotography outings. Next, you may recall from Chapter 3 that our outward view into the night is constantly changing as the Earth spins around its axis, so you may appreciate that we only see the moon during the 12 hours when it’s above the horizon in its current position! For example, while the waxing crescent moon, Figure 5.7(b) rises above the horizon in early morning and sets in the late afternoon or early evening; three weeks later, the moon will have orbited three-quarters of the way around the earth to position (h) in Figure 5.8 and entered the waning crescent phase. Now it rises well after midnight but sets in the afternoon! The schedule for the moon’s visibility, including the approximate rise/set times for each phase, are summarized in Figure 5.8(b); quite often people are surprised to learn that each month, there are days when the moon rises in the morning and sets at night, along with the sun!

5.8 (a) Here we see a typical monthly schedule for the phases of the moon, in this case for the month of July 2019, which begins with the new moon on July 2, 2019. (b) The approximate times when the moon is above the horizon for each phase is shown here, along with typical rise and set times.

Source: (a) PhotoPills

By the way, if all this doesn’t quite yet make perfect sense, don’t worry! It usually takes a while and some practice in the field before the full arrangement of the system begins to click. In fact, to facilitate your learning, why not try explaining the causes of the phases of the moon to a friend—I promise you will both learn tremendously during the process of doing so.

To summarize, see if you agree with the following true statements:

1. Half of the moon is always illuminated.
2. There is no permanently dark side of the moon.
3. The shadowed part of the moon is not the earth’s shadow.
4. The shadowed part of the moon is its own shadow.
5. The phase of the moon seen from Earth only depends on, and is caused by, the moon’s orbital position within its 29 ½ day cycle.
6. The moon rotates about its axis precisely once per orbital revolution around the earth.
7. Once a month (new moon), the side of the moon facing away from Earth is in full sunshine.

How Moon Astronomy Impacts the Timing of Landscape Astrophotography

Now you’re ready to apply your new knowledge of the astronomy of the moon in planning your astrophotography adventures. To do so, let’s consider five classic nightscape opportunities: (i) a nightscape with starry skies over a well-illuminated foreground, Figure 5.9(a); (ii) a moon halo or corona, Figure 5.9(b); (iii) a nightscape with a crescent moon, Figure 5.9(c); (iv) a dark sky Milky Way nightscape, Figure 5.9(d); and (v) a nightscape with a full moon rising or setting precisely over a specific landmark, Figure 5.9(e). The phase of the moon is absolutely critical in each of these images; attempting them during the wrong phase of the moon would only result in frustration and disappointment.

Starting with a dark sky Milky Way nightscape, Figure 5.9(d), you can now appreciate that we need the moon to be totally absent from the night sky, or well below the horizon, Figure 5.7(a), (b) and (h). Turning to your new understanding of the astronomy of the moon, you see that you must schedule your dark sky astrophotography excursion within 3–4 days of the new moon, as indicated in Figure 5.9(f). Similarly, for a nightscape image with a crescent moon as part of the image, Figure 5.9(c), you can now see that you will need to plan your outing to occur on the same dates, with the exception of the date of the new moon, when the moon will not be visible at all. Furthermore, by examining the position of the waxing crescent moon, Figure 5.7(b) in the days immediately following the new moon, you can see that it will only be visible setting near the horizon during late afternoon and early evening, Figure 5.8(b); the waning crescent moon, Figure 5.7(h) will only be visible rising near the horizon in the days immediately preceding the new moon during early morning before sunrise, Figure 5.8(b).

For a nightscape image showing a fully illuminated foreground and a sky richly populated with stars, as well as a moon halo, adequate lighting from a full, or nearly full, moon is required. Thus we need to select dates that are plus/minus 3–4 days of the full moon, Figure 5.9(f). Again, to select the time of day when the moon will appear as we desire, by examining the position of the waxing gibbous moon, Figure 5.7(d) in the days immediately preceding the full moon, you can see that it will be visible during the entire evening and early night, Figure 5.8(b), whereas the waning

5.9 Several classic nightscape opportunities and their corresponding phase of the moon: (a) a nightscape with starry skies over a well-illuminated foreground—best within 3–4 days of the full moon; (b) a moon halo or corona, best within a week of the full moon; (c) a nightscape with a crescent moon—also best within 3–4 days of the new moon, except for the day of the new moon; (d) a dark sky Milky Way nightscape—best within 3–4 days of the new moon; (e) a nightscape with a full moon rising or setting precisely over a specific landmark, which must be done on the day before, the day of, or the day after the full moon; (f) These nightscapes can be synchronized with the regular monthly cycle of moon phases, as shown here for the example of July 2020.

Source: (a) Oshin D. Zakarian/DreamView.net/The World At Night; (c) Babak Tafreshi/www.dreamview.net/www.twanight.org/The World At Night

5.10 (a) The deep red shadow of the earth falls on the full Blood Moon during this partial lunar eclipse over colorful birch fall foliage in the lake country of northern Minnesota. (b) The moon partly covers the sun during this partial solar eclipse. (c) This schematic shows the relative orientation of the sun, Earth, and moon during a lunar and solar eclipse. The earth is between the sun and the moon during a lunar eclipse, whereas the moon is between the sun and the earth during a solar eclipse.

gibbous moon, Figure 5.7(f) will only be visible at night in the days immediately following the full moon, and doesn’t rise until sometime well after sunset, Figure 5.8(b).

Finally, I’m sure that you can now appreciate that on the one day of the month during which the moon is full, the full moon must rise precisely at sunset and set precisely at sunrise, Figure 5.9(e) and Figure 5.7(e). This is the direct result of its orbital location—the moon is on the side of the earth directly opposite the sun. Similarly, on the dates of the new moon, or the time when the moon passes between the sun and the earth, Figure 5.7(a), the moon sets in the west and rises in the east, respectively, along with the sun and for all practical purposes is invisible. Thus, you can now understand that lunar eclipses, Figure 5.10(a), which occur when the earth moves between the sun and the moon and casts its shadow directly on the moon, must occur during the full moon. Similarly, partial and total solar eclipses, Figure 5.10(b), during which time the moon moves between the sun and the Earth, occur only on the day of the new moon!

Moonrise and Moonset

A special consequence of the timing of moonrise and moonset relates to the outstanding opportunity to capture the nearly full moon rising the day before or setting on the day of the full moon. At these moments, the moon can appear magically suspended in the earth’s shadow, Figure 5.11 or floating between the earth’s shadow and the Belt of Venus. Especially for the case of a Supermoon, or Harvest Moon, described next, these photo opportunities can be real prize-winners! A special note of hard-learned practicality however—the actual timing of the moment of moonrise relative to that of sunset/sunrise on these days can differ by 20–30 minutes from month to month, which can significantly impact the moon’s position relative to the earth’s shadow.

5.11 The Harvest Moon rises silently within the earth’s shadow over the hills of Southern California.

In fact, the specific moonrise/set when the moon rises in a position exactly straddling the boundary between the earth’s shadow and the Belt of Venus may only occur once per year! So carefully consult your planning tools to pinpoint that one day when your shot may present itself. Oh, and keep your fingers crossed for good weather!

Supermoon, Blood Moon, and Harvest Moon

You have probably heard of the “Supermoon,” or “Blood Moon,” and asked yourself what’s the big deal? The answers are more societal than scientific. Along with other astronomical phenomena, the full moon has always played a prominent role in human culture, and notable annual events like these have given us a reassuring sense of the regular cycles of nature. As shown in Table 5.1, there are a number of special designations of full moons. Each has its origin in a combination of astronomy and popular culture.

As one example, let’s consider the “Supermoon” designation, which in addition to appearing slightly larger than normal, has been credited with triggering natural disasters! Supermoons are full moon that occurs during the part of the moon’s orbit when the moon is in the closest physical proximity to Earth, or at its perigee. What’s that? As shown in the top view schematic of Figure 5.12, the orbit of the moon around the Earth isn’t perfectly circular, but is actually an oval, or an ellipse. As a natural consequence, there is one point when the moon is closest to (perigee) and one point when it is farthest away from (apogee) the earth, Figure 5.12(a). The difference in moon-Earth distance between these two points is about 50,000 km, which although not inconsiderable, only leads to a difference in apparent diameter of about 14 percent as well as a difference in apparent brightness of about 30 percent, Figure 5.12(b). This brightness difference isn’t especially significant, as you will see in Chapter 12. Nevertheless, each full moon can provide you with an opportunity to link the beauty of astrophotography with increasingly publicized popular culture.

5.12 (a) Schematic illustration (top view) showing the elliptical nature of the moon’s orbit around the earth (Not to scale). A natural consequence is that there are two points, apogee and perigee, when the moon is furthest away, and closest, respectively, to the earth (It is easy to remember—apogee = away). (b) The “Supermoon” occurs when the full moon coincides with perigee, but only results in an apparent diameter difference of 14 percent and a brightness increase of only 30 percent, or only approximately one-third EV.

Interactions of Moonlight with Water

We have been considering moonlight that reaches us through a transparent atmosphere. What happens if the moonlight hits water droplets or ice crystals along the way? The answers are moonbows and ice halos, respectively! Although relatively uncommon, both provide splendid opportunities to showcase beautiful and unusual sides of landscape astrophotography, Figure 5.13(a) and (b). As will be described in more detail in Chapter 10, moonlight undergoes wavelength-dependent refraction as it passes through suspended water droplets to produce beautiful, ghostly images whose colors are marvelously captured by the sensitive sensors in our cameras.

The ways in which moonlight reflects from standing bodies of water—oceans, lakes, and streams—provides yet another set of opportunities. The height of the moon above the horizon, or its altitude, coupled with the choice of lens and object distance can greatly affect the resultant images, Figure 5.14 (a) and (b). Careful planning for the phase of the moon along with knowledge of its location in the sky enables you to target your nightscape image with pinpoint precision.

5.13 Moonlight refracting through water droplets produces beautiful “moonbows”: from (a) falling rain in Northern Ireland and (b) spray from Yosemite Falls, California.

Source: (a) Martin McKenna/ www.nightskyhunter.com /The World At Night; (b) Vaibhav Tripathi/The World At Night

5.14 Light from the full moon reflects off Lake Superior to provide (a) a dramatic highlight to Split Rock Lighthouse along Minnesota’s North Shore; and (b) a serene backlight to the Aerial Lift Bridge of Duluth, Minnesota in wintertime. In (a), a wide-angle lens was used compared to the telephoto lens used in (b). These lens choices result in a very different appearance of the reflected moonlight within the composition.

The Moon Illusion

Finally, no discussion of moon astrophotography would be complete without explaining the phenomenon known as the “Moon Illusion.” The moon illusion refers to the purely psychological perception that the moon appears larger when it is nearer the horizon than when it has ascended high into the sky, Figure 5.15. When we see the moon next to objects on Earth that decrease in size as they increase in distance from us, we interpret the moon as being enormous! This happens simply owing to the decreasing size of terrestrial objects through parallax. Once the moon has risen into the sky with no reference points, its size appears to shrink.

5.15 The moon illusion is the purely psychological perception of an increase in the moon’s size when it nears the horizon. All three circles in this diagram have the same diameter, yet the one at the horizon appears larger simply owing to our minds tricking us. This same phenomenon happens when the moon is just peeking over the horizon; there is an illusion that it is unusually large!

You can use an index card with calibrated markings to “measure” the moon’s diameter the next time it is full in order to test this phenomenon for yourself, Figure 5.16. Be sure to hold the card at arm’s length in order to get a consistent measurement. Now, during this or the next full moon, measure the size of the full moon when it is both next to the horizon and when it is overhead. When you compare measurements, you will see they are the same!

5.16 Use an index card with different white gaps marked to “measure” the moon’s diameter the next time it is full. You can use this card with its calibrated measurement of the perceived size of the moon to select objects or the correct size that might be good subjects to juxtapose with the full moon, as in Figure 1.1(c).

An interesting outcome of this exercise is the ability to develop a handy field guide to estimating the size of the moon relative to possible foreground candidates that might be good subjects to juxtapose with the full moon, as in Figure 1.1(c). If you repeat the exercise above but simply with, say, the fingernail of one of your outstretched hands at arm’s length, you will be able to develop an estimate of the size in of the full moon in comparison to the width of the fingernail. For example, experience has shown me that the full moon is approximately half the width of the fingernail on the little finger of either hand when held outstretched at arm’s length. This knowledge has proved invaluable during day scouting trips in preparation for a rising full moon nightscape image. I simply hold up my hand at arm’s length, and compare the size of half the width of my fingernail to the size of the foreground object. If they are roughly the same, then I know that the rising full moon will appear to be of equivalent size.

One last point that should be made concerns the ability to photograph the details of the craters on the surface of the moon. These craters and mountain ranges are generally not possible to resolve even with common 100–300 mm lenses. Much higher focal length lenses, and even a telescope may be necessary. Also, exposure bracketing is often required to simultaneously record images with sufficient surface detail of the full, or nearly full moon but that are badly underexposed for the foreground, and images correctly exposed for the foreground, or stars, but that show the moon as an overexposed, featureless disc.