# On a lunar map, why is it labelled East on Earth, West on Moon?

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Why is east and west reversed for the moon? Why does north and south remain the same?

Imagine you're lying down outside, looking up at the sky, with your body aligned so your head is pointing North, and your Feet are pointing South. If you look to your Left, you'll be looking East, and see the East part of the ground and sky. If you look to your right, you'll be looking West, and see the West part of the ground and sky.

Now imagine a friend holds a globe above your head, centered on your home city, with the north pole pointing North, and the South pole pointing South.

When you look at your country on that globe, the parts East of your city will be on the right side of the globe, and the points west of it will be on the left side of the globe.

The same thing happens with the Moon. When you're standing on the Earth, looking up at the Moon near the meridian, from the Northern Hemisphere (so it appears generally south of you), The parts of the Moon that are Lunar-Surface-East of the Moon's center will appear on the right side, and the parts of the Moon that are Lunar-Surface-West will appear on the Left.

## Moon Atlas

Since 1961, the lunar coordinate system was set so that an observer located on the Moon would see the Sun rise in the East and set in the West, as on Earth. Consequently to an observer on Earth, the Moon's Eastern limb is to the West and the Moon's Western limb is to the East. As the vast majority of Moon references use this convention I have adopted it here too. In text discussing Moon images on this website, West means towards the Moon's Western limb (i.e. our Eastern horizon) and East means towards the Moon's Eastern limb (i.e. our Western horizon). By convention North is up. Unless otherwise stated, in the Image Gallery, North is up, East is right, West is left, South is down.

The VTM map of the Moon is divided into a 15 x 15 reference grid and nine maps. Each map links to the respective Image Gallery folder. Maps and their abbreviations: North West (NW|), North (N|), North East (NE|), West (W|), Central (C|), East (E|), South West (SW|), South (S|) and South East (SE|). Lunar features described below have a map and grid reference, e.g. Plato (101 km) N| G2 . Crater diameters are given in parentheses. Feature names are hyperlinked to respective images in the Image Gallery. Symbols ♠, ♥, ♦ and ♣ link to additional images. Map link returns to VTM map.

## Why this month's lunar eclipse could be extra special

The upcoming total lunar eclipse is setting up to be a spectacular viewing event for a few different reasons.

#### What You Need To Know

• A total lunar eclipse happens on May 26
• It will also be a supermoon
• The best view in the U.S. will be on the West Coast
• A partial solar eclipse happens in June

On May 26, 2021, most of the United States will see some or all of a total lunar eclipse.

A total lunar eclipse happens when Earth lines up between the sun and the moon. This eclipse may be even more incredible because the full moon will be a super moon.

This happens when the full moon is closest to the earth, so it appears larger.

Another reason we may get some great photos from this event: When the Earth casts a shadow on the moon, it can look darker and even red, so it's also called a Blood Moon.

This eclipse will be very special for the West Coast of the U.S., where they will see a total lunar eclipse.

The totality of the lunar eclipse will be about 14 minutes long near Los Angeles from about 4:11 a.m. through 4:25 a.m. that morning.

Other parts of the U.S. catch a partial lunar eclipse. For example, people in Raleigh, N.C. will see a partial eclipse for about an hour beginning around 4:45 a.m.

If skies are not clear and you miss out, you will have to wait a while for the next total lunar eclipse.

This month brings the &ldquomost super&rdquo of the year&rsquos supermoons, and on top of that, a total lunar eclipse. In other words, on May 26, 2021, the full moon will enter Earth&rsquos shadow &mdash and, when the Moon is not in our planet&rsquos shade, it will appear even bigger and brighter than usual.

### What is a supermoon?

The Moon travels around our planet in an elliptical orbit, or an elongated circle. Each month, the Moon passes through perigee (the point closest to Earth) and apogee (the point farthest from Earth). When the Moon is at or near its closest point to Earth at the same time as it is full, it is called a &ldquosupermoon.&rdquo During this event, because the full moon is a little bit closer to us than usual, it appears especially large and bright in the sky.

### What is a lunar eclipse?

A lunar eclipse takes place when the Sun and Moon occupy precise positions on opposite sides of Earth. During this alignment, Earth blocks some of the Sun&rsquos light from reaching the full moon. Our atmosphere filters the light as it passes, softening the edge of our planet&rsquos shadow and giving the Moon a deep, rosy glow.

### How can I see the supermoon eclipse?

Observers all over the world will be able to see the supermoon throughout the night if the sky is clear. Like all full moons, the supermoon rises in the east around sunset and sets in the west around sunrise. It is highest overhead in the late night and very early morning hours.

The lunar eclipse is harder to catch. The total eclipse, or the time when the Moon is in deepest shadow, will last for about 15 minutes. If the Moon is up in your area while this happens, you are in for a treat.

The total lunar eclipse will be visible near moonset in the western continental United States and Canada, all of Mexico, most of Central America and Ecuador, western Peru, and southern Chile and Argentina. Along the Asian Pacific Rim, the total eclipse will be visible just after moonrise.

The partial eclipse, which takes place as the Moon moves into and out of Earth&rsquos shadow, will be visible from the eastern United States and Canada just before the Moon sets in the morning, and from India, Nepal, western China, Mongolia, and eastern Russia just after the Moon rises in the evening.

Observers in eastern Australia, New Zealand, and the Pacific Islands, including Hawaii, will see both the total and the partial eclipse.

If the supermoon eclipse isn&rsquot visible from your location, you can still explore this phenomenon second by second with NASA&rsquos Scientific Visualization Studio.

### Why does the Moon turn red during a lunar eclipse?

Colors are one way for our brains to interpret variations in the physical properties of light. These same properties cause each color of light to behave differently when passing through a substance like air. If you&rsquove ever looked up at a blue sky, or savored a fiery sunset, you have seen this phenomenon in action.

Sunlight bends and scatters as it passes through Earth&rsquos atmosphere. In air, colors at the blue and violet end of the rainbow scatter more widely than colors like red and orange. Widely scattered blue light tints the sky when the Sun is overhead on clear days. Redder light travels a straighter path through the air we only see it scattered throughout the sky around sunrise and sunset, when sunlight has traveled through a thick slice of Earth&rsquos atmosphere before reaching our eyes.

During a lunar eclipse, some of this heavily filtered morning and evening light makes it all the way through Earth&rsquos atmosphere and eventually reaches the lunar surface. The eclipsed Moon is dimly illuminated by red-orange light left over from all of the sunsets and sunrises occurring around the world at that time. The more dust or clouds in Earth&rsquos atmosphere during the eclipse, the redder the Moon will appear.

### Are all supermoons red? Are all lunar eclipses supermoons?

No, and no. Supermoons and lunar eclipses are different phenomena that do not always occur at the same time. This month brings an excellent opportunity to enjoy the view.

## What you’ll see when the lunar eclipse happens

If sky conditions allow and clouds stay away, you’ll see a blood-red full moon and a spectacular show. As this will be happening around dawn in the mountain and Pacific time zones, the farther west you go, the darker the skies and deeper red the moon will appear. If you find yourself in Hawaii, the eclipse will be most dramatic, peaking shortly after 1am local time with a bright, red blood moon!

## Contents

Longitude on the Moon is measured both east and west from its prime meridian. When no direction is specified, east is positive and west is negative.

Roughly speaking, the Moon's prime meridian lies near the center of the Moon's disc as seen from Earth. For precise applications, many coordinate systems have been defined for the Moon, each with a slightly different prime meridian. The IAU recommends the "mean Earth/polar axis" system, [1] in which the prime meridian is the average direction (from the Moon's center) of the Earth's center. [2]

The selenographic colongitude is the longitude of the morning terminator on the Moon, as measured in degrees westward from the prime meridian. The morning terminator forms a half-circle across the Moon where the Sun is just starting to rise. As the Moon continues in its orbit, this line advances in longitude. The value of the selenographic colongitude increases from 0° to 359° in the direction of the advancing terminator.

Sunrise occurs at the prime meridian when the Lunar phase reaches First Quarter, after one fourth of a lunar day. At this location the selenographic colongitude at sunrise is defined as 0°. Thus, by the time of the Full Moon the colongitude increases to 90° at Last Quarter it is 180°, and at the New Moon the colongitude reaches 270°. Note that the Moon is nearly invisible from the Earth at New Moon phase except during a solar eclipse.

The low angle of incidence of arriving sunlight tends to pick out features by the sharp shadows they cast, thus the area near the terminator is usually the most favorable for viewing or photographing lunar features through a telescope. The observer will need to know the location of the terminator to plan observations of selected features. The selenographic colongitude is useful for this purpose.

The selenographic longitude of the evening terminator is equal to the colongitude plus 180°. [3]

## What is Earth’s shadow, and when can you see it?

View at EarthSky Community Photos. | Stephanie Longo captured this image on the morning of February 2, 2020, at Eleven Mile Canyon State Park in Colorado. She said: “I was treated to a display of Earth’s shadow and the Belt of Venus over the Continental Divide. The mountains of the Divide were a little too far away for a quick shot and my fingers were painfully numb, so I decided on shooting this large hill named Spinney Mountain.”

Like all worlds orbiting a sun, Earth casts a shadow. Earth’s shadow extends about 870,000 miles (1.4 million km) into space. You might not realize it, but, from Earth’s surface, you can see the shadow. In fact, it’s easy to see, and you’ve probably already seen it, many times, as day changes to night.

That’s because night itself is a shadow. When night falls, you’re standing within the shadow of Earth.

The best time to watch for Earth’s shadow is when it’s creeping up on your part of Earth … Like all shadows, the shadow of Earth is always opposite the sun. So you’ll want to look eastward after sunset for the shadow (or westward before sunrise).

Earth’s shadow is the dark blue line above the horizon in this photo by Jörgen Andersson in Sweden. View larger. | Night falls when the part of Earth you’re standing on enters Earth’s shadow. Image via NASA.

The shadow is a deep blue-grey, and it’s darker than the blue of the twilight sky. The pink band above the shadow is called the Belt of Venus.

The shadow of the Earth is big. You might have to turn your head this way and that – along the arc of the horizon opposite the sun – to see the whole thing. And, just so you’ll recognize it more easily, remember that the shadow is curved, in exactly the same way that the whole Earth is curved.

And, once you spot it, don’t go back inside just yet. Wait awhile, and watch Earth’s shadow ascending in the east at exactly the same rate that the sun is setting below your western horizon.

Earth’s shadow is the blue line near the horizon, behind the bare trees, in this November 2017 photo by Alice McClure. The pink band above the shadow is the Belt of Venus. You don’t have to be in a country location to see Earth’s shadow. Sucheta Wipat caught the Earth’s shadow and Belt of Venus on a cloudy August evening in London.

Earth’s shadow extends so far into space that it can touch the moon. That’s what a lunar eclipse is. It’s the moon within Earth’s shadow.

When the sun, the Earth and the moon are aligned in space (nearly or perfectly), with the Earth between the sun and moon, then Earth’s shadow falls on the moon’s face. That’s when people on Earth see the shadow gradually turn a bright full moon dark in a lunar eclipse.

As seen from Earth’s surface, there are typically two or more lunar eclipses every year. Some are total, some are partial, some are a subtle kind of eclipse known as penumbral.

During a lunar eclipse, a very small amount of light from the sun filters through Earth’s atmosphere onto Earth’s shadow on the moon. It’s why – at the middle part of a total lunar eclipse – the shadow on the moon looks reddish.

Eclipse guru Fred Espenak in Arizona – whose calculations of eclipses have been a mainstay of eclipse observing for decades – wrote of the January 31, 2018, total lunar eclipse: “What a wonderful total lunar eclipse! This was my 30th, and the 1st one I’ve seen where the moon set during totality.” Mike O’Neal submitted this gorgeous shot of the January 31, 2018, lunar eclipse. He wrote: “Could not quite get to full before the clouds rolled in over northeastern Oklahoma.”

Another way to get an awareness of Earth’s shadow is simply to think about it as seen from space.

The image below provides a beautiful global view of Earth at night. It’s a composite image, assembled from data acquired by the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite over nine days in April 2012 and 13 days in October 2012.

The dark part is, of course, Earth’s shadow.

Bottom line: Look for Earth’s shadow in both the evening and morning sky. It’s a blue-gray darkness in the direction opposite the sun, darker than the twilight sky. The pink band above the shadow – in the east after sunset, or west before dawn – is called the Belt of Venus.

## Moon Phases Visualized – Where Is the Moon?

The Moon phases visualization shows the positions of the Moon and Earth in real time. Distances are not to scale.

The Sun is not shown, however, the Earth's illumination indicates its position to the left. Because of the Earth's axial tilt, the Sun's assumed location shifts up and down slightly over the course of the year in this animation, appearing on the same horizontal plane as the Earth solely during the March and September equinoxes.

The circle shows the Moon's anticipated path in the upcoming weeks, including the next 3 or 4 Moon phases. As the Moon's position varies from one revolution to the next, the arrow indicating the expected lunar path may not point exactly towards the Moon's current position.

The arrows displayed after the Illumination, Distance, and Latitude values indicate their downward or upward trend.

Note: This is a beta service. We welcome feedback and error reports.

#### Planet Sizes and Order

How large are the planets and what is their order from the Sun?

#### Distance, Brightness, and Apparent Size of Planets

See how far the planets are from the Sun or Earth, how bright they look, and their apparent size in the sky.

## Lunar Observations

Summary: Perhaps the most popular object in the sky, and one which provides a truly magnificent view through the telescope, is the moon. Its surface is covered with interesting features that reveal much about its history, and indeed about the history of the Earth-Moon system. To the naked eye, some of the more pronounced features visible as light and dark areas have been likened to the face of the "Man in the Moon." Binoculars and telescopes reveal countless craters on the surface of the Moon. These craters are the scars left by of ancient impacts by large meteorites, most of which occurred 3-4 billion years ago.

In the Moon lab, you will make observations of the moon, sketch features that you see, draw deductions about the moon based on your observations, and determine the dimension of the moon and of major features. This is a fairly long lab and may take more than one lab period to complete. The Moon is by far the celestial object with the richest details when viewed through a telescope. You will become familiar with the surface of the Moon by completing this lab. Take time to observe the countless details that it offers. The Moon may be a dead world, but it is a complex world nevertheless.

Note: You should make observations and sketches and to discuss what you are doing with your lab partner and classmates. The calculations can be done outside of lab time, based on the data you collect during lab. Similarly, you should discuss during lab time how to answer questions posed in this lab, but you should write down your answers outside of lab time. Everything goes into your observing log.

This lab involves a lot of sketching that can take a lot of time. For this lab only, you and your lab partner can share your sketches. The rules for sharing observations are:

• Each parter must do about half of the sketching required
• You include your partner's sketches as photocopies (not hand-drawn reproductions)
• You explicitely label each sketch with the name of its author

Failure to follow these 3 rules will constitute a case of plagiarism.

After you have completed the observations for this lab, answer the questions, based on your observations and discussion with your lab partner and classmates. Consult your your textbook for help and explanations if it includes a section on the Moon.

Near and Far Sides of the Moon: Refer to the map of the moon provided by your TA. Note that Earth-based photographs always show the same side of the moon. Because the moon's rotational period is the same as its period of revolution with respect to the stars (the sidereal period), only one side of the moon ever shows its face to Earth. This side is known as the near side. The other side, known as the far side, has only been seen directly by a few astronauts during the Apollo missions.

### Procedures

Date and Phase: Record the phase of the Moon as seen with the naked eye using the templates provided. Also draw the features that you see with your naked eye. Note the date, time and sky conditions.

With the telescope: Point the telescope at the moon and, with the 25 mm eyepiece, locate some of the features listed on the maps. The current phase may limit the areas that can be seen. Observe the smooth dark areas on the moon. Because the appearance of these regions reminded early astronomers of the smooth oceans, they are known as maria (the Latin term for "seas"). The rougher and brighter areas are known as highlands.

Maria and highlands: List all the maria that are visible. Contrast the smooth, dark maria with the light, rough highlands. The surface of the moon is composed mostly of basaltic rock, a typical rock formed from the cooling of molten lava. However, the basaltic rock of the maria contains a lot of iron, giving rise to the dark color. On the other hand, the highland basalts contain much aluminum. Because of this difference in composition, the maria have a greater density than the highlands. You don't have to sketch at this point but take good notes!

Terminator: Next, observe the terminator, the "line" separating sunlight from darkness on the moon. Switching to the 10mm eyepiece, draw a sketch of a small region of the terminator that you find interesting. Take the time to make a careful sketch that actually looks like what you see. Label the main features on your sketch.

Question: Comment on how some aspects of what you see are different along the terminator than elsewhere on the moon. Describe and explain the differences.

Craters peaks: Identify one of the following craters: Agrippa, Delambre, Eratosthenes, Langrenus, Theophilus, or Tycho. In order to magnify the crater, replace the 25 mm eyepiece with the 10 mm eyepiece after centering. Draw a sketch of the crater and the mountain in the center of the crater, and any other features that may be physically associated with the crater. Take your time and do a good job!

Question: Looking at the surface of the Moon in general, locate several craters with central peaks and several without. Is there a pattern between these two types of craters?

6. Crater rays: Find one of the following craters: Aristillus, Copernicus, Langrenus, Kepler, Pickering or Tycho. Do not use the same crater you used in #5. Notice the bright rays radiating from the crater. These rays are much brighter a times near the full Moon.

Question: What do you think may have caused these rays?

More Craters: Next locate either Plato, Facastorius, Ptolemy or Letronne. Again, magnify the image by viewing with the 10 mm eyepiece. and sketch the crater. You may see tiny craters peppering the floor of these large, flat craters.

Question: In what way(s) is this crater different from the others you have been looking at. Notice especially the color on the inside of the crater walls. What other features on the moon share this same color?

Crater density and the relative ages of highlands and maria: One of the most important ways astronomers have learned about the moon, the history of the earth, and the history of the entire solar system is by crater counting,'' i.e. by comparing the numbers of small and large craters on different regions of the Moon and other bodies in the solar system. This can be done by counting the number of craters of various sizes on a given part of the Moon's surface. If youassume that the rate of crater-forming impacts on the Moon has remained constant since its formation, variations in crater densities imply variations in the ages of formation of the surface. Compare the crater densities of the highlands and maria and deduce which kind of terrain is youngest.

Question: If you now consider that the rate of crater-forming impacts has decreased over time (is we know is the case), would the age of the highland and mare surfaces be closer to each other or even more different than under the assumption of constant crater formation?

How big is the moon? Measure the diameter of the moon using one of the two following methods:

The method of transit times. This method works only if you can time a transit of the full diameter of the Moon, something that can be done only near the Full Moon or when the earthshine is fairly strong. Switch the telescope drive off and measure the time T (in minutes) it takes for the entire diameter of the moon to drift across one edge of the field. Also note the current declination of the Moon, d,based on its position in the sky and the SC001 star chart. Using the expression used in the field of view lab, obtain the apparent diameter the Moon, a (in minutes of arc):

a=T cos(d) x 15'

At other time the method of transit times would give only the thickness of the phase of the Moon, which is not particularly interesting in itself. If you can't use the method of transit times for a full lunar diameter, then you can use a somewhat less precise method based on the field of view of the telescope. Using the 25mm eyepiece and knowing its field of view in minutes of arc (see your results from the field of view lab), estimate the diameter of the Moon to the nearest minute of arc by simply comparing their relative sizes visually.

The small triangle formula enables us to determine the diameter of the moon (dMoon) if we know the angular size a (which we just measured) in minutes of arc and the distance to the moon (DMoon), according to the formula:

Using radio signals, we know that the average distance between the center of the earth and the center of the Moon is DMoon = 384,000 km. Provided that the diameter of the Moon is much smaller than 384,000 km, this formula will be a valid method for determining dMoon. Note that the number 3438' corresponds to the number of minutes of arc in an angle of 1 radian and that 360 o =2*pi radian.

Question: What is the diameter of the Moon, dMoon in km?

Question: Is the small triangle approximation we just used reasonable?

Question: How does the diameter of the Moon compare with the diameter of the Earth and to the East-West extent of the contiguous United States? To do this, compute the ratio dMoon / dEarthand dMoon/LUSA and comment.

You can do the final calculation of dMoon outside of class.

What shapes are craters? Select a few craters that are similar in angular size, selecting some near the middle of the moon, some part way to the lunar limb (the curved edge of the moon), some as close to the limb as you can find. Identify the craters and sketch their outlines only (i.e. general shape) and estimate how far away each crater is from the center of the disk of the Moon, using the apparent radius of the Moon as you unit of measure. For example, a crater at the center would be at a distance of 0, a crater halfway between the center and the limb would be at 0.5 and one right on the edge would be at 1.0. Put this number next to your sketch, along with the usual information (date, time, scale, orientation, sky conditions, etc).

Question: Do the craters appear to change shape, moving from the lunar center outwards toward the limbs? If so how does the shape change?

Question: Why should or shouldn't the apparent shapes of craters change or be the same as ne moves from the center toward the limb of the Moon?

Question: What can you deduce about the shape of the moon based on these observations of apparent shapes of lunar craters?

More Observing. The table following the procedures lists some of the most interesting features visible on the surface of the Moon, including mountains, craters, rays, valleys and canyons. Become familiar with them by identifying and observing at least 8 features of various types. Takes notes on each of them (i.e. describe their appearance).

Sketchin reasonable detail examples of three different types of features. Add to your sketch the dimension of each feature in minutes of arc and in km using the method of transit time to measure its apparent East-West size. Simply time how long the feature takes to cross the edge of the field of view (with the telescope drive off) and use the above formulas. Comment on the size (in km) of the features you measure.

The Lunar Limb. Now focus your attention to the lunar limb, the round edge of the Moon. Notice how the edge is not perfectly smooth. Make a sketch of a small portion of the limb that shows some jaggedness. Take notes. What are you really seeing?

Men on the Moon. Use the second table and the lunar map to identify at least two of the Apollo lunar landing sites. While no trace of the landings are visible through any Earth-based telescope, take a moment to look at the spot and reflect on these historical events that took place three decades ago. You can add personal thoughts and comments to your logbook.

### Craters, Rays & Mountains

Notes: Selenographic (i.e. lunar) longitude and latitude are defined in fashion very similar to their geographical equivalents. The meridian zero (longitude=0 o ) is defined as the meridian that crosses (N-S) the middle of the visible hemisphere of the Moon. Selenographic latitude is measured from the lunar equator, which pretty much runs across (E-W) the middle of the disk. Thus, the central point on the lunar disk is at position (0E, 0N). East and West are defined for an observer standing on the Moon (cartographic convention, just like on Earth) and are reversed from the astronomical directions in the sky.

Name Sel. Long. Sel. Lat. Comments
Langrenus 62E -9 Large crater near the lunar limb
Petavius 60E -26 Rima Petavius, running from the central peak to the rim is an unusual feature. Best seen when the Moon is young.
Messier & Messier A 47E -2 This pair of craters probably formed simultaneously by a broken/binary impactor. Note the comet-like double ray extending from Messier A. Were these two craters caused by a grazing impact?
Proclus 47E +16 Small crater with a very bright ray system on the edge of Mare Crisium.
Fracastorius 33E -23 Flooded crater with collapsed N wall
Theophilus 26E -11 Relatively young crater overlapping Cyrillus
Altai Mtns 25E -25 Battered mountain range with sinuous scarp
Ariadaeus Rille 13E +6 Long, straight canyon''
Cassini 5E +40 Two smaller craters inside give it an unusual appearance.
Hyginus Rille 6E +8 Long, narrow rille (canyon'') with a bend and a superimposed crater (Hyginus). Terrain to the North has many smaller grooves.
Alpine Valley 2E +49 Long, flat valley in the lunar Alps Mountains
Apennines Mtns 0 +18 Beautiful and complex chain of mountains
Mt. Piton 1W +41 Isolated mountain peak in Mare Imbrium
Ptolemaeus 2W -9 Large, round crater with dark floor. How many small craters can you see on its floor? Ptolemaeus is so wide (90km) that if you were standing at the center, you wouldn't see the crater rim as it would be below your horizon!
Archimedes 4W +30 Large crater with flat floor
Rupes Recta 8W -22 The "Straight wall" is a cliff that is 80 km long and 300 m high.
Mt. Pico 9W +46 Isolated mountain peak in Mare Imbrium
Plato 10W +52 Flat lava-flooded crater with dark floor. Can you see very small craters on its floor?
Tycho 11W -43 Young crater with the most extensive ray system on the Moon.
Eratosthenes 12W +14 Young crater at the S end of the Apennines Mtns. Compare to the larger Copernicus.
Stadius 14W +11 "Ghost of a crater", flooded by lava during the formation of Sinus Aestuum. Only the upper part of the rim is visible.
Clavius 14W -58 Very large, very old crater with many smaller craters superimposed (Seething Bay).
Montes Recti 20W +48 Small chain of mountains at the edge of Mare Imbrium
Copernicus 20W +10 Young crater. Note: central peaks, terraces inside wall, structure of outer slopes, chain of craterlets to the NE. About 60 km across, roughly the size of Davidson county.
Kepler 38W +8 Very bright ray system, visible to the naked eye!
Gassendi 40W -18 Floor criss-crossed by cracks
Schroter's Valley 50W +55 Deep "canyon" near crater Aristarchus
Grimaldi 68W -6 Large crater with flat, dark floor. Best seen near full Moon
High mountains -- near South pole This region shows the largest vertical relief on the Moon. These mountains and crater rims are seen sideways and reveal their true elevation. Compare with your perception of relief along the terminator.

### Apollo Landing Sites

Mission/Date Sel. Long. Sel. Lat. Comments
Apollo 11 (7/20/69) 23.5E +0.7 Between craters Sabine and Moltke
Apollo 12 (11/19/69) 23.5W -3.0 Between craters Fra Mauro and Lansberg
Apollo 14 (2/5/71) 17.5W -3.7 Just North of Fra Mauro
Apollo 15 (7/30/71) 3.6E +26.1 At the North end of the Apennines Mtns
Apollo 16 (4/21/72) 16.0E -9.0 In the lunar highlands, W of crater Theophilus, just north of crater Descartes
Apollo 17 (12/11/72) 30.8E +20.2 In the Taurus Mtns, near crater Littrow

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## Supplemental Materials

Lunar phases are interesting, but we can look closer! The line that divides light from darkness on the Moon is called the terminator. If you were standing along this line on the Moon, you would see either a sunrise (waxing moon) or a sunset (waning moon.)

Challenge your students to look up photos of the different phases of the Moon online. Look along the terminator and you will see dramatic shadows cast by mountains and craters. Look farther away from the terminator and the Moon appears much more flat, few shadows are to be seen. Can your students explain why this is so?

Hint: Near the terminator, the Sun appears low in the lunar sky. Like sunrise here on Earth, the shadows are long and dramatic. Farther away from the terminator, the Sun is well overhead. Like noon time here on Earth, shadows are shorter and less noticeable. Go outside in the early morning – and again at noon time – your students will easily see the difference!

### Being an Astronomer

Being an astronomer means first being a careful observer. It works best if you can consult a lunar calendar. Many calendars have little symbols on them indicating full, new, and quarter phases, there are also a variety of free apps for your smartphone that will do the same thing. Plan this initial observation for the time of the first quarter moon phase the Moon will be easily visible at sunset (students won’t have to stay up late!) and remain in the sky for a few hours making it an easy target for everyone.

Have students trace a circle on a piece of paper and draw a horizontal line below it like the one shown here. Ask them to go out in the back yard with a parent after sunset and sketch the Moon’s appearance inside the circle. Hold the paper up so that the horizontal line matches the horizon before they draw to get the orientation correct if they can. (Some teachers may wish to simplify the activity by eliminating this step for younger children.) Emphasize to the students that all they need to observer is the shape of the lighted portion of the Moon’s surface (just the phase). Understandably, some children may wish to sketch or color in some of the light and dark regions of the lighted portion of the Moon – don’t discourage this, but emphasize that an accurate sketch of the Moon’s shape is the first priority.

If you have older students who have access to smart phones, some of them may wish to try and capture a photograph of the Moon with their phone camera. Don’t discourage them from trying, this is perfectly safe, but far more difficult than it may at first appear. The Moon is a tiny target, smaller than a typical aspirin tablet held at arm’s length! It is also very bright, and on a dark background, making it difficult for most cameras to focus on. Street lights and lights from nearby autos will make it even more difficult, and just holding your hand steady enough to capture this tiny target may well be beyond the skills of most elementary age children. Although it may seem strange, sketching by hand is in this case, much easier than taking a photo!

Once your students have made a single sketch of the Moon at night, ask them to match it to the lunar phase model they have created. Once they have done this, ask them to predict which phase will come next, and how many days this may take to happen.

One of the most powerful things about a scientific model of theory is that it gives us the ability to predict what will happen in nature. This model will give your students the ability to predict the behavior of the Moon, and then the skill set needed to observe and verify their prediction. This is extremely powerful! Your students, even very young children, can learn to function as scientists by observing nature, constructing models, and then making and verifying their predictions.

In spite of the low cost and simple methods used in this activity, the outcomes are sophisticated and powerful. Our students have become scientists. They have the power to predict nature, and the ability to frame and ask even more complex and profound questions. When we, as teachers, highlight and celebrate their achievements in STEM science by doing activities like this, we not only initiate them into the sciences, but armor them against misconceptions later in life.

### Being a Scientist

Making a scientific model and exploring it in the classroom is a wonderful activity, but this is only half of what a scientist does. After making a shiny new model and playing with it for a while and thinking up lots of new ideas and questions, it is time to take this baby out for a spin! Let’s compare what the model tells us to what we see in nature! This critical step, which we call an experiment, will tell us if our model is any good or not. A good model is sometimes called a theory, and it will do two important things. First, our model will be able to predict the behavior of nature and help us to know what happens next. Second, our model will point us toward new knowledge by helping us to ask clever questions that lead to further discoveries. Now, it’s time to get started!

### Following Up:

Ask your students what is good or powerful about this model we have created? You are likely to get a variety of answers, but sooner or later a student will zero in on the idea that this model allows us to predict the behavior of the Moon as it orbits the Earth and to measure time without a clock or calendar. Point out to them that the ability to predict the lunar phases and keep a calendar was a major accomplishment for ancient societies, and that most modern people can’t do it without help either!

Playing with and exploring the lunar phase model has no doubt inspired many questions among your students. If you have written down and answered some of them, this is the time to go back and draw your student’s attention to the fact that playing with the model inspired both questions and learning! Real scientists value scientific models for just this reason!

Now ask your students what is weak or wrong about this model? Where does it fail? This may be a difficult question for young children they are not used to considering where or how something fails in a dispassionate way. Failure is synonymous with BAD! Not so for the scientist!

Lead them to consider questions like What? When? Where? Why? How? Our model tells us whatwill happen next, but it does not tell us why it happens, or how it works. It is true that our model fails to give us all the answers we desire, but this is a fundamental truth about all scientific models. Many students hear the word “science” and they begin to think of a great, all-knowing body of knowledge or an omniscient scientist figure. Nothing could be further from the truth!

Every scientific model explains some things, but not others. A model or theory may answer some questions (What lunar phase comes next?), but will likely fail to answer others (How do lunar phases work?). Students need to learn that science is not infallible! For instance: it is incorrect to say that science has proven something. Scientific models never answer all of our questions – there is always something new to learn or discover, even about the things we’ve known the longest.