From the June 2019 issue

Target Apollo landing sites

Even a small scope can help you pinpoint these six famous locations.
By | Published: June 21, 2019
The line that divides the Moon’s light and dark regions is called the terminator. It’s where lunar sunrise (between New Moon and Full Moon) or sunset (between Full Moon and New Moon) happens. The terminator is visible whenever the Moon is visible and not full.
John Chumack
Pointing a telescope at the Moon is an easy way to get into the immensely rewarding pursuit of amateur astronomy. Luna offers something perfect for observers of all skill levels and with all sizes of telescopes: a face that’s always changing. Following the Moon through a lunar month — from its first appearance as a New Moon in the evening sky to its next such appearance — will demonstrate its dynamic nature like no book or magazine article can. The Moon is easy to find, and you can view it even under strong light pollution. And unlike the Sun, it’s completely safe to look at with the naked eye.

The 50th anniversary of Apollo 11 is the perfect time to view the places where the Apollo astronauts landed. If you’re a Moon watcher — and even if you’re not — you need to check these six sites off your lifetime observing list. While no telescope, not even Hubble, can pick out the actual Apollo hardware that remains on the lunar surface, it’s not hard to find the half-dozen spots where 12 moonwalkers made history.

NASA called the Apollo 11 landing site “Tranquillity Base” because the craft touched down in Mare Tranquillitatis, the Sea of Tranquillity. Six craters form an easy-to-find pattern that leads you to the site. Once you’re in the area, look for the three craters named for the mission astronauts. Because the biggest (Armstrong) is only 2.9 miles (4.6 kilometers) in diameter, you’ll need a large scope to spot it. This region is visible four through 18 days past New Moon. Note that, as with all these areas, shadows will be sharper and detail will be more evident at the beginning and end of that range.

All IMAGES BY NASA/JSC/Arizona State University UNLESS NOTED

When and where to look

Ironically, the worst time to view the Moon is when it’s Full and at its brightest. That’s when the Sun’s light hits our satellite straight on, which minimizes the shadows and reveals scant detail.

There are two prime times for lunar viewing. The first one lasts from when the thin crescent becomes visible after New Moon until about two days after First Quarter (in the evening sky). The second one lasts from about two days before Last Quarter to almost New Moon (in the morning sky). Shadows are longer then, and features stand out in sharp relief. This is especially true along the Moon’s shadow line — called the terminator — that divides the light and dark portions. Before Full Moon, the terminator shows where sunrise is occurring; after Full Moon, it marks the sunset line. So, when you’re looking at the Moon, the terminator is where most of the action is.

The Apollo 12 landing site lies within the Moon’s huge Oceanus Procellarum, the Ocean of Storms. Because this feature covers 812,000 square miles (2.1 million square km), we need to refine our search a bit. First, locate Lansberg Crater, then find the triangular group of craters to its lower right. The landing site lies midway between Lansberg and the largest of the triad. This region is visible 10 through 24 days past New Moon.
Along that shadow line, you’ll see mountaintops protruding high enough to catch sunlight, while dark, low-lying terrain surrounds them. On large crater floors, you can follow “wall shadows” cast by the sides of craters hundreds or thousands of feet high. What’s more, these features change in real time, and you can see striking differences in just one night.

Two-part landscape

Scientists differentiate features on the Moon between lighter areas, called highlands, and darker features, called maria (the Latin word for seas). The dark material inside maria is solidified lava, and it dates back to periods of volcanism that ended about a billion years after the Moon formed (which happened some 4.5 billion years ago).

But the lava isn’t even the oldest part of the Moon. That honor goes to the highlands, which consist of ancient lunar surface rock and materials thrown out during previous explosive impacts. The highlands are a Moon watcher’s treasure-trove of mountains, valleys, bright areas, and shadows.

Then there are the craters. Of the 9,144 named features on the Moon, 8,737 (nearly 96 percent) are either craters (1,624) or satellite features (7,113). (Satellite features are small craters outside the main ones that carry the main crater name plus a letter — for example, Archimedes M.)

Many more craters dot the highlands because these areas have been around longer than the maria, which were resurfaced by their volcanic activity. Craters range in size, so a fun way to challenge yourself is by noting the size of the smallest crater you can see. 

You might have already spotted the Apollo 14 landing site without knowing it. Apollo 14 landed about 5° to the right of the Apollo 12 site as we view the Moon, or a scant 1/36 of our satellite’s apparent diameter. Nudge your scope to the right a bit, and center the double crater at the center of this image. Those two impacts are craterlets (small craters formed from material blown out of a crater during its formation) of Fra Mauro, which lies just below the bottom of this image. This region is visible nine through 23 days past New Moon.

The Apollo 15 landing site is quite close to Archimedes Crater. Ease your scope’s field of view a bit to the right and down some. When you see the sinuous rille, or valley, Rima Hadley — a feature that looks like a 50-mile-long (80 km) winding, dry river — you’re there. This region is visible seven through 21 days past New Moon.

A few tips

The Moon is a bright object, and it’s even brighter through a telescope. Many observers use a neutral density filter to cut down the light. Manufacturers sell small ones that screw into the barrels of eyepieces.

If you don’t have access to such a filter, try these two methods of reducing the Moon’s brilliance: high magnification and a device called an aperture mask. The first restricts the field of view by magnifying it so that you’re looking only at a small area of the lunar surface, thereby reducing the amount of reflected sunlight. The second is a simple cardboard mask with a small hole cut out of it. If you cover the front of your telescope with it, less light will get through, and it will be like using a smaller scope. If you’re using a refractor, you can center the hole. For reflectors and catadioptric scopes, you’ll need to offset the hole from the center, so it doesn’t fall atop the secondary mirror. If you have a reflector, which uses four metal vanes to support the secondary, place your cardboard mask so the hole is between two of the vanes.

For those who want the best possible view of the Moon, turn on a white light behind or beside you as you sit at the telescope. As long as you can’t see the light directly, the placement doesn’t matter. Adding ambient light suppresses your eye’s tendency to adapt to the dark and causes it to use normal (daytime) vision, which is of much higher quality than night vision. This definitely is not what you want if you’re looking at a deep-sky object, but it works on the Moon because it’s so bright.

To locate the Apollo 16 landing site, aim your telescope just to the lower right of the Moon’s center, then view this region, which lies north of Albufeda Crater. The distance of the landing site from Dollond Crater is the same as that crater’s distance to Descartes Crater. This region is visible six through 20 days past New Moon.
When observing large craters, note whether you can see “rays” emanating from them. These tendrils of ejecta formed when crushed rock sprayed out after an impact. Rays appear as light, radial streaks, and they can lie a great distance from the crater. For a good example, point your scope toward the Copernicus impact crater.

Scope out the Moon

Now you’re ready to head outside, set up a telescope, and search for the Apollo landing sites. The best way to start is to familiarize yourself with each of the six images of those regions you’ll find in this story.

Do note, though, that your scope might produce images that are upside down, flipped, or both. So, you might need to rotate the appropriate page. For scopes that flip images left to right, it might be best to photocopy each image, then shine a light on the front of the page while you look through the backlit side.

With these maps as starters, tracking down the spots where humans walked on the Moon might be easier than you think. Take your time, have fun, and good luck with “one small step” into lunar observing

The Apollo 17 landing site lies in the Moon’s northeastern (upper right, as we see it) quadrant. The site’s name, Taurus Littrow, refers to Littrow Crater in the Taurus Mountains, just on the eastern (right) edge of Mare Serenitatis. When you find Littrow Crater, look just below it, slightly outside its southern wall. This region is visible four through 18 days past New Moon.