Come fly with me to Mercury


MESSENGER flies over Mercury. The spacecraft blasted off from Cape Canaveral on August 3, 2004.

To commemorate this week’s 10th anniversary of the launch of NASA’s MESSENGER spacecraft to Mercury, NASA released this amazing video of a flight over the planet’s north polar region. The movie was assembled from 214 images taken once per second by the probe’s narrow-angle camera on June 8, 2014. Enjoy the cratery desolation.

As the photos were snapped, MESSENGER orbited at altitudes ranging from 71 to 102 miles (115 to 165 km), traveling at a speed of 2.3 miles per second relative to the surface.

One of the highest resolution pictures ever taken of Mercury’s surface shows a field of craters only 1.8 miles (3 km) wide photographed on June 11, 2014. MESSENGER will drop down much closer to the planet – only 31 miles – starting August 19. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

“This view is what a traveler on the MESSENGER spacecraft might see during low-altitude operations in the coming year,” said MESSENGER co-investigator Scott Murchie. “During the final phase of its mission, MESSENGER’s science instruments will use low-altitude operations like this to explore the surface and subsurface of Mercury at unprecedented resolution.”

Mercury is presently too close to the sun to see safely, but on August 2 it lined up in conjunction with Jupiter as seen through the coronagraph (sun-blocking device) on the Solar and Heliospheric Observatory. Credit: NASA/ESA

Mercury orbits closest to the sun of the eight planets, completing one revolution every 88 days. It has virtually no atmosphere and measures only about a thousand miles larger than Earth’s moon.

Daytime surface temperatures there can reach 801°F (427°C). Despite the extreme heat, MESSENGER’s instruments detected water ice in permanently shadowed craters in the planet’s polar regions.

Launched in August 2004, MESSENGER traveled 4.9 billion miles (7.9 billion km) to finally settle into orbit around the speedy planet on March 18, 2011. Its convoluted journey included 15 trips around the Sun and flybys of Earth once, Venus twice, and Mercury three times. All of this was done to slow the craft down so it could enter orbit about the planet. It’s returned more than 240,000 pictures so far, many of which you can browse HERE.

Supermoon fun / Mars-Spica conjunction tonight / Venus visits Mercury at dawn

Passing clouds create a colorful corona around last night’s full moon. Credit: Bob King

The moon coaxed many of us out for a look last night. We had clear if hazy skies in my town which made for a striking display of lunar crepuscular rays. Lunar what? If you’ve ever seen sunbeams poking through clouds in the afternoon or evening, you’re looking at crepuscular rays. Crepuscular comes from the Latin word for ‘twilight’ as the beams are often noticed during early evening hours around sunset.

A delicate display of crepuscular rays radiates across the sky above a cloud-shrouded moon. Credit: Bob King

Bright rays shining through gaps in the clouds alternate with shadows cast by other clouds to form a spreading fan of light and dark columns. The dustier or smokier the air, the more vivid the crepuscular display. Notice how they appear to converge on the moon. This is an optical illusion. The rays are perfectly parallel just like endless rows of beans on a farm that appear to merge together in the distance.

Last night’s supermoon shines back from a mobile phone. I took the picture by holding the phone’s camera lens directly over the eyepiece. Credit: Bob King

Many of us like to take pictures of the moon through a telescope using nothing more than a mobile phone. If you’ve tried this, you know how tricky it is to hold the phone camera in the right spot over the telescope eyepiece. It takes a few tries, but the results can be remarkable. Phones do well on bright celestial object like the planets, moon and sun (with a safe filter). Despite what some ads might tout, phones can’t yet record fainter things like galaxies, nebulae and the like.

Orion Telescopes makes an adaptor to hold a phone securely over the telescope. While it gets mixed reviews, you might want to consider it if you don’t want to invest in a separate camera but would still like to create an album of your own astrophotos.

Mars (top) and Spica last night July 12. The difference in color between the rusty planet and blue-white star was very easy to see. Mars will remain near the star the next few nights but change its position like the hour hand on a clock. Credit: Bob King

I know we’ve all been moonstruck the past few nights, but did you happen to notice how close Mars and Virgo’s brightest star Spica have become? Last night they were separated by only 1.5 degrees; tonight they’ll be in conjunction a squinch closer at 1.3 degrees. Watch for the duo in the southwestern sky near the end of evening twilight.

Mars moves eastward and soon departs Spica en route to its next notable appointment, a conjunction with Saturn on August 25. Have you been up at 5 a.m. lately? Me neither. But my crystal ball a.k.a. Stellarium program tells me that Venus and Mercury are playing tag an hour before sunrise in the eastern sky.

Venus and Mercury shine together low in the northeastern sky during morning twilight the next couple weeks. This map shows the view tomorrow morning 45 minutes before sunrise. Venus will be about 10 degrees (one ‘fist’) high, Mercury half as much. Source: Stellarium

Mercury reached greatest elongation (distance) west of the sun yesterday and now appears about five degrees high in the northeast some 45 minutes before sunrise. Look for it about the same distance below brilliant Venus. This is a good apparition of Mercury, and having Venus nearby makes it easy to spot.

The swiftest-moving planet will hang near the goddess planet for the next two weeks, all the while growing in brightness as its phase fills out from crescent to full.

Crescent moon visits a ‘wintering’ Venus / Mercury-moon conjunction for y’all

The slender crescent moon brushes Venus Tuesday morning at dawn low in the northeastern sky. The Pleiades star cluster, better known as the Seven Sisters, floats just above the pair. This map shows the sky facing northeast around 4 a.m. June 24. Stellarium

Wonder where the moon’s been hiding lately? Unless you’re up around 3 a.m. it’s been scarce this past week. All that time our favorite cratered world has been slimming down in the morning sky.

Now it’s a waning crescent fingernail, what many consider the moon’s most eye-catching phase.

Tuesday morning June 24 at dawn the thin crescent will join Venus in the constellation Taurus just below the pretty Pleiades star cluster. About 1 1/2 degrees or three moon diameters will separate Venus and the moon. To see this beautiful conjunction, look low in the northeastern sky at the start of dawn.

For the best view of the Seven Sisters, I recommend binoculars. Whenever I’ve had a reason to be up before sunrise in early summer I make a point of looking at the cluster. Taurus, neighboring Auriga and the Pleiades all belong to the winter sky, but we get a preview of that inevitable season as early as the first mornings of summer. There’s something delicious about seeing the first stars of winter as the robins sing in the dewy woods.

An extremely thin moon will pass very close to Mercury on Thursday morning June 26 as seen from the southern U.S. This view shows the sky facing northeast right around sunrise for New Orleans, LA. The moon will only be about 5 degrees high at the time. Use binoculars to find it. Seeing Mercury will require a small telescope. Stellarium

Live in the far southern U.S.? You’ve got one more lunar visitation. This one will be challenging. On Thursday morning, the moon, just 21 hours before new, will glide a fraction of a degree south of the planet Mercury in a bright sky only minutes before sunrise. The moon will hover very low (5 degrees) in the northeast in a bright sky. Whatever you do, bring binoculars. You might need them to find the moon at all.

Like the moon, Mercury’s an extremely thin crescent and very faint, shining at just magnitude 3.5. Skywatchers might spot it in binoculars, but I’m not betting on it. With very clear skies, there’s a chance of seeing the planet directly above the northern cusp of the moon with a small telescope. Should you succeed, you’ll be rewarded with the rare sight of two delicate crescents one atop the other. Find a location with a wide open view to the northeast and start looking about 15 minutes before sunrise.

The moon will cover up or occult the planet for observers in northern South America, but again, this will happen in a bright sky and prove tricky to see.

Just a reminder. Although no auroras showed last night at mid-latitudes, there’s still a chance for a minor storm tonight. I’ll send out a notice if that happens.

 

Lunar crescent returns – Mercury and Jupiter follow mother sun into twilight

The crescent moon will be near Mercury tonight (May 30) and below Jupiter tomorrow night. The map shows the sky facing northwest about 40 minutes after sunset. Stellarium

Nice to see to moon back in the evening sky just in time for the weekend. The 2-day-old slender slip of a thing makes an appearance about 40 minutes after sunset about 7 degrees (not quite one outstretched fist) to the lower left of Mercury.

Keen-eyed observers with haze-free skies may spot the planet without optical aid, but I’m guessing it will take a pair of binoculars. Mercury has faded in the past few weeks and will soon disappear in the sunset glow not to return again for northern hemisphere skywatchers until mid-July before dawn.

You’ve probably noticed that Jupiter’s been dropping lower and lower in the west and now sets near the end of evening twilight. The hefty planet and skinny moon will line up for one last easily visible conjunction tomorrow evening. By next lunar crescent (June 29), Jupiter will be difficult to pick out from the twilight glow.

In this map I’ve removed the atmosphere and added the ecliptic, the path taken by the sun, moon and planets across the sky. The sun’s day-by-day travel to the east is a reflection of Earth’s revolution around the sun. Its movement outpaces that of the outer planets, so it gradually catches up and then passes them one after another. When near the sun, a planet can’t be seen, but when the sun has left it behind, the planet reappears to the right or west of the sun in the morning sky to start the cycle all over again. Stellarium

Because sun, planets and moon all follow the same general path across the sky called the ecliptic, they inevitably pass near the sun for at least a few weeks every year (more often for the inner planets Mercury, Venus and the moon). Solar glare renders them invisible for a time until they pop back into view in the morning sky at dawn and begin the next cycle of visibility.

Saturn disappears, Mercury appears during ‘night of the planets’


Saturn covered and uncovered by the moon earlier today by Dave Herald, Murrumbateman, Australia

Enjoy the video. Dave Herald did a great job recording this morning’s Saturn occultation. The images are very sharp. I always find it remarkable how atmosphere-less the moon is. There’s not a hint of softness in the planet as it’s devoured by the lunar limb. If there were substantial air, the planet would gradually soften and fade.

For a moon or planet to be completely without air is next to impossible. The solar wind knocks atoms from minerals on the lunar surface and sends them reeling into the virtual vacuum above the surface. Studies have found potassium, sodium, helium and argon in the moon’s exosphere, the name given to the lunar atmosphere. Bombardment of the moon’s surface rocks by micrometeorites and the solar wind release potassium and sodium; helium and argon probably bubble up from radioactive decay of those same rocks. Helium may also arrive via the sun’s wind.

Glow from sodium in the lunar atmosphere. The light from the moon has been blocked by the telescope, but the size, position and phase of the Moon are shown by the superimposed image in the center. Rayleighs are a measure of brightness. Credit: NASA

At sea level on Earth, we breathe in an atmosphere where each cubic centimeter contains 10,000,000,000,000,000,000 (10 quintillion) molecules; by comparison, the lunar atmosphere has less than a million molecules in the same volume.

Comets and meteoroids striking the surface temporarily enhance the amounts of other atoms and molecules. But the sum total of all the sputtering and interacting is an atmosphere equal to the amount of air you’ll find 250 miles high where the space station plies it orbit. Not much.

Mercury stands all by itself low in the northwest in this photo taken about 50 minutes after sunset last night. Credit: Bob King

At my house, we saw no occultation of Saturn, but the two did stand together in the southeastern sky at dusk. On the opposite end of the heavens, Mercury made a fine naked eye appearance in the northwestern sky.

Jupiter glows over Amity Creek last night. Both the creek and the sky were lit by the light of the full moon. Credit: Bob King

I first caught it around 9:15 p.m. some 40 minutes after sunset and watched it for at least a half hour. Capella and Jupiter – both higher up in a darker sky – made for great sight lines to the planet.See yesterday’s map for details.

Jupiter in Gemini remains the most brilliant object in the western sky at dusk during early evening hours. I watched it from a nearby creek that rushed with water from snow melt and recent rains.

Mars stood between Jupiter and Saturn. This week the ‘boring’ hemisphere – the one with fewest dark markings – is turned toward western hemisphere observers.

The Moon, Mars (upper right), Saturn (lower left), Spica (immediate right of moon) and Arcturus (top) as seen from Dayton, Ohio on May 12. Credit: John Chumack
Dayton, Ohio

But there’s still much to see – enough to easily stay up past your bedtime. The north polar cap on Mars remains visible despite the seasonal summer ‘heat’, and white clouds topping the planet’s major volcanoes are visible along the planet’s western edge. Check it out.

Mercury leaps into dusk – don’t miss it!

The sky facing west about 40 minutes after sunset in mid-May when Mercury will be just shy of one outstretched fist above the northwestern horizon.  It shines brightly at magnitude -0.3 this week. Use higher, brighter Jupiter to make a sight line to the planet. Mercury’s making its best evening appearance of the year for northern hemisphere sky watchers. Stellarium

Now through the end of May is the prime time to look for Mercury in the evening sky. Like the rock star Prince, this small, speedy planet is elusive, making only a few brief appearances a year.  Consider this a personal invite to the show.

To find Mercury, pick out a place with a wide open view to the west-northwest in the direction of sunset. Start looking a half hour after sundown about a fist to the left of the brightest glow left on the horizon by the setting sun. Mercury will be some 8-10 degrees (about one outstretched fist) above the horizon. It looks like a solitary diamond in twilight’s pink glow.

Mercury shows phases as it revolves around the sun as seen from Earth’s perspective outside looking in. Mercury, like Venus, appears largest when nearly lined up between Earth and sun at inferior conjunction. Planets not to scale and phases shown are approximate. Illustration: Bob King

Mercury gets easier to see as the sky darkens … to a point. Once it’s within a few degrees of the horizon, the thicker, dustier air in that direction quenches its light and the planet fades.

The one-day old evening crescent moon with Mercury (upper left) on Jan. 31 this year. Credit: Bob King

It’s amazing that Mercury’s rates as a planet considering how small it is – just 3,021 miles (4,880 km) in diameter. At 2,160 miles across, our own moon is 71% as large. Jupiter’s moon Ganymede is even bigger at 3,275 miles (5,270 km). If it were orbiting the sun instead of Jupiter, Ganymede would easily be considered a planet. Pluto, demoted to dwarf planet status in 2006, spans just 1,430 miles (2,302 km).

Despite Mercury’s diminutive dimensions, its self-gravity easily crushed it into a sphere long ago. That plus the fact that it revolves around the sun and has cleared its orbit of competition from other smaller bodies places it firmly within the realm of the planets.

And there’s no planet quite like it. Mercury hovers near the sun too close to see and a few weeks later leaps into the morning sky. Drifts back down toward the sun in a few weeks and then leaps into the evening sky. So it goes, back and forth like that a half dozen times a year. Northern hemisphere observers see it best at dusk during late winter and spring ‘elongations’ and at dawn in the fall.

It’s easy to guess the reason for its swift maneuvering – a tight orbit around the sun lasting only 88 days keeps Mercury on the move.

Mercury looks like a tiny gibbous moon this week through a small telescope. Use at least 75x to make out its shape.  Illustration: Bob King

Like Venus and the moon, Mercury shows phases. Right now, if you’re lucky enough to train a telescope on it before it atmospheric turbulence near the horizon mushes up the view, the planet would look like a very tiny gibbous moon 66% illuminated.

Its phase changes quickly too. Within a few weeks, as it moves closer to Earth and grows in apparent size, the planet will morph from gibbous to half to a dim crescent. Yes, dim! Mercury is brightest when at ‘full moon’ phase, being nearly as brilliant as Sirius, but fades to 3rd magnitude when a thin crescent. This week we’ll see it brightest; next week the planet will start to fade noticeably.

Orbiting between 28 and 43 million miles (46 and 70 million km) from the sun and possessing no atmosphere, Mercury’s temperature ranges from an extremely hot 800 F (430 C) on the dayside to marrow-chilling -280 F (-170 C) on the nightside.

To the eye, Mercury would appear as shades of dark brown. NASA enhanced the subtle colors to in this photo of the planet, a mosaic of images taken by MESSENGER. Younger craters with their bright rays appear blue. Plains formed form ancient lava eruptions are tan or orange. Credit: NASA

Because the planet’s axis is tilted only .01 degree – it essentially rotates straight up and down perpendicular to the sun – sunlight never reaches into craters in its polar regions. Locked in permanent shadow, NASA’s MESSENGER spacecraft has found strong evidence for abundant water ice and other volatile materials stored there for millions of years.

We could go on and on about this strange little planet, but I’d be holding you back from getting outside to see it for yourself. For more information, check out NASA’s quick-facts summary and a wonderful gallery of photos from MESSENGER.

Mercury returns, planets align, life is good

Mercury is just entering the picture tonight but by May 10 it will be easy to see, along with three other evening planets, 45 minutes after sunset in the northwestern sky. The pink arc is the ecliptic, the apparent path the sun takes during its yearly travels. It’s also followed closely by the planets and moon. Click to enlarge. Created with Stellarium

Planets are popping up everywhere. We’ve touched on Jupiter and Mars many times the past few months, but recently Saturn and now Mercury have entered the scene. Maybe you’ve noticed Saturn now in the southeastern sky at nightfall. From the northern U.S. and southern Canada, it’s bright but low at nightfall. Saturn reaches opposition a week from now when it will be at its closest and brightest for 2014. Each night that passes, the ringed rises higher and becomes better placed for viewing.

Mars, brilliant and fiery orange-red, now dominates the southern sky before midnight, standing above fainter Spica in the constellation Virgo. Only a month past opposition, we’re smack in the middle of the best time to observe the Red Planet through a telescope. I try to catch a look every clear or partly cloudy night but nearly missed the chance last night.

Two different hemispheres of Mars. The left image from May 2 shows a shrinking north polar cap and clouds blanketing the base of several volcanoes (dark dots) along the left edge of the planet. Right view taken on April 14 shows the hemisphere currently facing U.S. observers at nightfall. Credit: Christopher Go (left) and Anthony Wesley

The sky suddenly cleared after almost a week of overcast. I figured I’d walk my dog first and then set up the telescope, but 15 minutes later, clouds reappeared in the west. I turned around and footed it back home as quickly as I could, catching just five minutes of Mars light before a blanket of clouds suffocated the starry sky. Yeah, it was worth it.

Jupiter on May 2 displays its two most prominent belts visible in small telescopes, the North and South Equatorial Belts. Credit: Christopher Go

You might think it’s crazy to look at a planet night after night. Amateur astronomers do this for several reasons. First, most nights the air is too turbulent for a clear, sharp view. Looking often maximizes your chances of seeing the planet crisply in stable air. Almost nothing in observational astronomy beats viewing Mars or Jupiter or Saturn without air currents gooing things up. At these special times the dross falls away and the planet looks absolutely real. No exaggeration, you feel like you’re right there.

Planets also rotate. One hemisphere faces us one night, another on a different night or different time of night. Repeated observation gives you a certain familiarity with the “landscape” and alerts your eye to any changes happening. Remember, on most planets, weather plays a role in their appearance. Unexpected changes like a newly-spawned dust storm on Mars or the disappearance of a cloud belt on Jupiter lend an air of anticipation to the night’s viewing.

The sky from the central U.S. facing west-northwest this evening May 3 about 25 minutes after sunset. Mercury will be very low (about 3-4 degrees) but bright. The crescent moon passes just north of the star Eta in the constellation Gemini. Stellarium

Let’s talk about Mercury a minute. Skywatchers blessed with a clear view down to the west-northwest horizon can find the little planet as soon as this evening. Face the sunset direction about 20 minutes after sunset and sweep a few degrees above the horizon with your eyes or a pair of binoculars. The planet now shines at magnitude -1.4 or nearly as bright as it can, an equal to Sirius, the brightest star.

If you don’t succeed, try again in a week on the 10th. After the late January show, the period from May 10-23 will be the best time this year to see the planet at dusk.

Ultra-thin moon dares you to find it tonight

A super skinny crescent moon as seen 20 minutes after sunset from the northern U.S. tonight April 29. The moon will be just 3 degrees or about a held horizontally at arm’s length above the horizon. Nearby Mercury will require binoculars if you see it all. Stellarium

Thanks to the moon’s repeating cycle, a wonderful observing challenge presents itself tonight. An ultra-thin crescent moon only hours old will squeak into view above the west-northwest horizon only minutes after sundown.

Fresh from this morning’s Antarctica eclipse, the moon will be just 18 hours old viewed from the East Coast, 19 from the Midwest, 20 from the mountain states and 21 from the Pacific Coast.

The one-day old evening crescent moon with Mercury (upper left) on Jan. 31 this year. Credit: Bob King

Others might be into extreme energy drinks, but I get jazzed up over extreme moons. My personal record is just shy of 24 hours, and it was surprisingly easy. Northern hemisphere late winter and early spring are the best times to catch a young moon at dusk because its angle to the horizon is very steep. Within a day after new moon, the crusty crescent already stands high enough above the setting sun to spot in the darkening sky.

Nothing quite compares to the delicacy of a hours-old moon. Spider webs and finely blown glass come to mind. The moon’s so thin you’d think it could break to pieces. Binoculars will show that it’s anything but smooth. Crater shadows cast across the precious sliver of moonscape give it a choppy, uneven appearance.

Here’s what you need to meet the challenge. Find a place where you can see as far down to the west-northwest horizon as possible and start watching at sunset. To maximize viewing time, click HERE to find out when the sun sets for your location.You’ll only have about 20-30 minutes before the moon drops too low to see through the haze. Bring binoculars and focus them on a very distant object – clouds are best – so the moon will be sharp when you eventually come across it.

Now sweep slowly above and left of the sun for a sign of the crescent. When you find it, lower the glass and try to see it with your eyes along. If you’re really lucky, you might even spy Mercury, now returning to the evening sky for one of its best appearances of the year. We’ll drop by the planet in a week or two. For now, the moon’s the apple of our eye.

Mercury and the sliver moon meet tomorrow at dawn

The thin moon and Mercury tomorrow morning about 30 minutes before sunrise. When you search for it, point your binoculars at the moon and then slide to the lower left to find the planet. Once you know exactly where to look, lower the binoculars and try to see it with your eyes alone. Stellarium

Not one day after Venus and the moon paired up so beautifully, Mercury gets a visit from an skinnier crescent moon tomorrow morning Feb. 27. Seeing the two will take a little more effort than this morning’s duo because they’ll be noticeably lower in the east-southeastern sky, and Mercury’s not nearly as bright as Venus. Still, if you have a clear view in that direction, it’s worth looking if only to see the delicate appearance of the moon.

All John Chumack had was a point and shoot camera when he grabbed this photo of the moon and Venus in a break in the clouds over the campus of the University of Dayton this morning. Credit: John Chumack

Once you’ve found the crescent, glide your gaze a few degrees to its lower left to find the innermost planet Mercury. The planet shines at first magnitude – reasonably bright – but has to fight bright twilight. That’s why binoculars are recommended to get started.

A sampling of craters named after artists and writers on the planet Mercury. Credit: NASA

One of the things I enjoy about Mercury is the naming system for its craters. A quick glance across a map of the planet reveals the names of deceased musicians, artists and writers from around the world. It makes me smile to see some of my favorites composers like Aaron Copland and Bela Bartok and French photographer Eugene Atget memorialized by impacts. Even Walt Disney’s up there.

Mercury brightens as March opens and also moves a little farther up and away from the sun, making it a bit easier to see, but you’ll have to go on it on your own then with no moon to guide the way.

Chasing lunar crescents … and Mercury too!

A sight worth the frozen fingers. The wafer-thin crescent moon alongside Mercury (upper left) over the Duluth, Minn. – Superior, Wis. area last night during twilight. The planet was visible for more than 1 hour 15 minutes after sunset. Details: 150mm lens at f/2.8, ISO 400 and 1/4″ exposure. Credit: Bob King

Hope you saw the pairing of Mercury and the 1-day-old moon last night. If you missed it or had to put up with bad weather, a slightly thicker crescent will hover a “fist” above Mercury in the western sky during twilight tonight. Start looking about 40 minutes after sunset.

The wiry moon sets over Duluth’s Spirit Mountain ski hill – many of the runs were lit up Friday night. Notice the prominent earthshine or darkly-lit moon. This is light reflected off Earth and out to the moon, where it’s reflected back again to our eyes. Details: 350mm lens at f/4.5, ISO 800 and 1-second exposure. Credit: Bob King

Be sure to catch the planet sometime in the next week before it slinks back toward the horizon and disappears in the twilight glow. The moon was so thin that its Cheshire cat smile appeared slightly broken or irregular to the eye. Sure wish I’d brought binoculars for a closer look.

Beautifully composed shot of Venus and the morning crescent on Jan. 28, 2014 on either side of a statue of astronomer Nicholas Copernicus at the Adler Planetarium in Chicago, Ill. Copyright: Don MacKay

One day before new moon phase, lots of folks reported sightings of a similarly skinny crescent to the lower left of Venus in the dawn sky. I received a couple beautiful images to share with you. Enjoy.

One day later on Jan. 29 the moon had moved to the left and below brilliant Venus. This photo taken from the woodlands of Lakewood Township near Duluth, Minn. Details: 1.6 sec, 70mm F4, ISO 400. Credit: James Schaff

Illustration (not to scale) showing why the evening crescent faces one way and the morning crescent the other. As the moon orbits the Earth, sunlight illuminates its left or eastern edge before new moon. After new moon, the right or western edge is lit. Illustration: Bob King