Astronomy

How bright is the full Earth during the lunar midnight?

How bright is the full Earth during the lunar midnight?


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At lunar midnight (i.e. the new moon as seen from Earth), the Earth is in its full phase with its entire disk in sunlight, and it is the brightest object in the lunar sky. How bright is it, and how variable is its brightness?

More precisely, I'm interested in specific figures for the magnitude and in comparisons to similar objects. Would I be able to read in that light? To drive? Would I notice the variations in brightness? What are the main variations due to?


Let's take an average albedo for the Earth of 0.3 (it depends, which hemisphere is visible, how much cloud cover etc.). That means the Earth reflects 30% of the light incident upon it.

The flux $f$ falling on the Earth is given by $$ f_{odot} = frac{L_{odot}}{4pi d^2} = 1.369 imes10^{3} Wm^{-2}$$ where $L_{odot}=3.85 imes10^{26} W$ from the Sun and $d= 1$AU.

The integrated luminosity from the illuminated hemisphere will be $$L_{earth} = 0.3pi R^2 f = 5.2 imes10^{16} W$$

So now we can compare this with the Sun. One hemisphere of the Sun radiates $1.93 imes10^{26} W$, and produces a flux of $1.369 imes10^{3} Wm^{-2}$ at 1 AU. Therefore the illuminated hemisphere of the Earth results in a flux of approximately $f_E=0.056 Wm^{-2}$, assuming the average Earth-Moon distance of 384,400 km. This calculation assumes isotropic emission, but it is quite likely that the albedo is higher for light reflected through 180 degrees.

The Sun has an apparent magnitude of -26.74, so the magnitude of the "full-earth" at the moon is $$ m_{Earth} = 2.5log_{10}left( frac{f_{odot}}{f_{E}} ight) - 26.74 = underline{-15.77}$$

The answer will of course vary with the albedo of the visible hemisphere, which in turn depends on the time of year and how much of the polar regions can be seen (e.g. http://www.climatedata.info/Forcing/Forcing/albedo.html ). Variations of a few hundredths seem possible, which will lead to apparent magnitude variations in $m_{Earth}$ of $sim pm 0.1-0.2$ mag. The albedo may also vary in detail with the exact angle at which the sunlight hits the Earth - an "opposition surge" in brightness, when the Sun-Earth and Moon are almost aligned is possible. The Earth-Moon distance varies from 363,000 to 405,000 km. This will lead to magnitude variations of $pm 0.12$ mag.

A further way to check this is that the albedo of the Moon is 0.12 and it has a radius of 0.273 times that of the Earth. Therefore the Earth seen from the Moon ought to be $(0.3/0.12) imes(1/0.273)^2 = 33.5$ times brighter. This is 3.81 magnitudes brighter. The mean magnitude of the full Moon is -12.74 (maximum is -12.92), so the brightness of the "full Earth" should be -16.55 on average.

I am not sure why these figures don't agree; I suspect it is that the albedo for reflection when the Sun's light is normally incident on the Moon is quite a bit larger than 0.12. The so-called "opposition surge". If the Earth's albedo behaves in the same way, then the latter figure may be more accurate than my first calculation. My gut instinct is that the answer is somewhere between the two.


Ask Ethan: How bright is the Earth as seen from the Moon? has some detailed explanations, including discussions of lunar eclipses as seen from the moon. It doesn't include magnitude calculations, but it concludes that

a “full Earth” as seen from the Moon is about 43 times brighter than the full Moon is as seen from Earth. When the icecaps are larger and the cloud cover is greater - and also when the deserts are visible in the Sun - the Earth appears at its brightest, up to approximately 55 times brighter than the Moon.

log(43) to the base 2.512 is 4.1, which when subtracted from the full moon's mean magnitude of -12.7 yields magnitude -16.8. Using the "55 times brighter" figure would lead to a maximum brightness of -12.7 - 4.4 = -17.1.

It doesn't seem to cover the effects of the distance between the Earth and Moon, so it might get even brighter at perigee.


January 2019’s Total Lunar Eclipse and the Flat Earth

The night of Sunday–Monday, January 20–21, 2019, there was a total lunar eclipse visible across the Western Hemisphere. We had planned an eclipse-watching event at Johnson Observatory here at the Creation Museum that night. But concerns about the very cold temperatures and safety at the observatory for our guests prompted us to cancel it. We had much rain on Saturday, followed by several inches of snow overnight. Then after the snow came very frigid temperatures—the temperature fell throughout the day Sunday, and it was in single digits Fahrenheit by the beginning of the eclipse. Consequently, there was much ice and snow around the observatory where we would have watched the eclipse. That wouldn’t have been safe for our guests.

However, the sky was mostly clear much of Sunday and into the night. So, I watched the eclipse from my home. I set up the observatory’s portable 3.5-inch Questar telescope in my driveway to which I attached my digital SLR camera. I made many trips between the inside of my house and the telescope outside. Besides taking photographs of the eclipse, I also watched the eclipse with just my eyes and with binoculars. A lunar eclipse is one of those astronomical events that doesn’t require a telescope.

Of the more than 200 photographs that I took, I was most pleased with this 13-second exposure that I took during totality. It captures something close to what I saw with the naked eye. Total lunar eclipses are rarely so dark as to make the moon disappear. Typically, the moon assumes some shade of red or orange. This color results as the earth’s atmosphere refracts light into the earth umbra, or shadow. Refraction not only bends light, but it also disperses it into various colors. The earth’s atmosphere also scatters light, but it does so differently at different wavelengths, or colors, of light. These two processes, refraction and scattering, combine to produce reddish hues in the earth’s umbra that are different at each lunar eclipse. I would describe most total lunar eclipses that I have seen as pumpkin or copper. This one was a bit odd because of its shade of red and because the color varied across the moon. I struggled to find a good description, but my research partner, Ron Samec, came up with a good one—strawberries and cream.

There have been reports of a meteoroid impact on the moon during the eclipse. From what I’ve seen, the impact showed up on videos and visually as a brief flash of light about the time that the total phase began. Unfortunately, I neither was looking at the moon nor took a photo at the time, so I didn’t see it. Even if I had taken a photo then, the impact likely would not have shown up.


The great lunar eclipse of 2018

This month there will be a spectacular total lunar eclipse partially visible from the UK. The date for your diaries is the evening of Friday, 27 July.

Lunar eclipse in 2004. Photo: Robin Scagell

The Moon will rise fully eclipsed, so we won’t see the early stages of the event. But that will actually add to the spectacle, because the Moon will be a deep red colour against the blue sky (assuming of course it’s good and clear!) The media are calling it a ‘blood Moon’ – though that’s not a term astronomers traditionally use!

A lunar eclipse, just to remind you but you really knew anyway, happens when the Moon goes into the Earth’s shadow, so it goes from being the familiar bright moon to a very dark one. As well as being interesting to watch, lunar eclipses can be very beautiful because of the unusual colours that occur.

Lunar eclipses explained

Normally during a lunar eclipse the Moon starts out as a regular full Moon, a complete disc, but then we start to see its left-hand edge become gradually darker until it seems to have a circular bite taken out of it. This is quite different from the phases of the Moon, caused by the Sun shining on it from different angles as the Moon goes around the Earth every month – starting with a crescent, then going to a half Moon, then gibbous when it’s nearly a complete disc, then Full. A lunar eclipse can only take place at full Moon, because that’s when the Sun is exactly opposite the Moon in the sky. In fact, the true full Moon always rises exactly opposite the Sun, and at the time the Sun is setting. And it doesn’t happen at every full Moon, because more often than not the tilt of the Moon’s orbit means that it goes above or below the Earth’s shadow.

So to continue the story of the eclipse, which takes place over a matter of a few hours, eventually the Moon is completely within the Earth’s shadow, so all the Sun’s light is cut off. But it doesn’t go completely black. There’s always a bit of light refracted around the edge of the Earth, even when the Sun is completely covered by the Earth. If you could stand on the Moon during a total eclipse you’d see the Sun gradually being hidden by the Earth’s larger disc, but even when it’s totally behind the Earth there would be red light bent around by our atmosphere.

Stages of a lunar eclipse. The Moon moves from right to left through Earth’s shadow, though it moves from left to right during the evening

The Sun’s light would have to travel through a lot of atmosphere to reach the Moon, so its becomes reddened – we see this every sunset, when the Sun’s light passes through the lowest and densest parts of the atmosphere. So being on the Moon would be like seeing all the sunsets around the Earth at once.

No human has stood on the Moon during a total eclipse, but in 1967 a spacecraft on the Moon, Surveyor 3, did photograph the event with its black and white camera. It showed that some parts of the atmosphere were brighter than others. Where there was a lot of cloud, it was dark. So if all the parts of Earth at the rim as seen by the Moon happened to be cloudy, the eclipse would be dark, and if they were clear, it would be bright. Another thing that affects the brightness is whether there have been any major volcanic eruptions in the past year or so. The eruptions in Hawaii and Guatemala might make this eclipse darker.

The total lunar eclipse of 24 April 1967 seen from the lunar surface by Surveyor 3. The Earth appears with a bright ring of light around its darkened surface as seen from the Moon. Photo: NASA/Galaxy Picture Library

After totality, the Moon slowly comes out of the deep shadow, called the umbra, and eventually starts to go through the paler outer shadow, the penumbra. Eventually it leaves the shadow completely and shines at its full brightness again.

What to expect

So what will we see on Friday 27 July? The Moon will rise as usual, around 9 pm BST (the exact time depends on where you are in the UK). And it will be exactly opposite the Sun in the sky. But instead of being bright and easily visible, assuming there are no clouds of course, it will be dark and red. Just how dark we can’t say. It could be completely invisible, or it could be deep red or orange in colour. The Moon usually is yellowish or reddish when it rises anyway, because it’s so low in the sky, but on this occasion it will be a much deeper colour. Maximum eclipse is at 9.21 pm, when the Moon is only a few degrees above the south-eastern horizon as seen from the south-east of the UK, though from the north-west the Moon doesn’t rise until around 9.30 pm.

The exact rising position also depends on where you live. From central England the azimuth (measured from north through east) is 122º, while from northern Scotland it is 127º. Tip: Use Google Earth’s Path tool to draw a line at this azimuth from possible observing sites to see which works for you.

Total lunar eclipse of 16 September 1997, when the Moon rose during the total phase of the eclipse. Photo: Robin Scagell/Galaxy

But around 30 minutes after sunset it should be easier to find, as it gets higher and the sky gets darker. It will probably be a very deep red, and even non-Moon watchers will realise that this is a very unusual appearance. Then the left-hand edge of the Moon will start to get a bit lighter until at 10.13 pm sunlight starts to return to the rim of the Moon and the total eclipse becomes a partial one. Over the next hour or so the dark shadow slowly leaves the disc, and by 11.19 the Moon is only in the outer shadow, so it just appears darker than usual at the right-hand side. By half past midnight it’s all over and the Moon is back to being a full white disc again.

You’ll be able to see the eclipse from anywhere in the UK, though you’ll need a clear south-eastern horizon to see the earlier stages when it’s rising. And from about 10 pm you’ll see the planet Mars right below it, appearing red itself because Mars really is red.

The timings

Moon enters penumbra (Earth’s outer shadow) 18:12 BST (not visible from UK)

Moon enters umbra (Earth’s dark inner shadow) 19:24 (not visible from UK)

Totality begins (Moon fully within umbra) 20:30 (not visible from UK)

Moon leaves penumbra 00:30

How the eclipse will progress on 27 July. From the UK the Moon doesn’t rise until around mid eclipse

Although at least part of the eclipse will be visible from all over the UK, how much you see of it will depend very much on where you live. The farther south and east you are, the better. From Dover, the Moon rises at 20:42 BST, and by mid totality it will be 4º above the horizon, but from Manchester the Moon is only 1.4º altitude at mid eclipse. From most of England and Wales the Moon has risen by mid eclipse, but from Scotland and Ireland the Moon rises after mid eclipse.

The eclipse will be an eerie sight, with the red totally eclipsed Moon barely visible as it rises, within a few minutes of sunset. How well it will be visible will depend on how clear the sky is. The Moon at this time of year is low in the sky and appears large, so could be very photogenic with a suitable foreground.


Stay up late - or get up early - for spectacular lunar eclipse

A lovely total lunar eclipse will be visible throughout the Bay Area and all of California before dawn Tuesday morning as the Earth's shadow darkens the bright full moon, and wherever skies are clear, it will be a time to look upward wide-eyed.

Astronomers say the eclipse should be a beauty, but only people willing to stay up very late or set their alarm clocks for long after midnight will see it.

It will last for a full hour and a half, and during that time, the moon's color could be anything from a dull and dusky red-brown to a reddish or even orange glow, depending on how much dust, pollution and mist is in the atmosphere, according to Andrew Fraknoi, chair of astronomy at Foothill College in Los Altos Hills, who has observed many in his time.

For the wide-awake, a partial eclipse will start at 1:51 a.m. Tuesday and become total starting at 2:52 a.m. By 4:22 a.m., the total phase will be over, but then as the moon begins to emerge from Earth's shadow, another partial phase will begin. The eclipse will end at 5:24 a.m., just as the sky lightens at dawn.

Lunar eclipses take place when the full moon and the sun are opposite each other in space, and the Earth in between them casts its shadow over the bright moon's face. But even when the eclipse is total, some indirect sunlight manages to reach the moon. The earth's atmosphere filters out most of the sun's blue light, leaving only the red frequencies to light the lunar surface.

"Since the moon is always safe to look at and the eclipse only makes the moon darker, there's no danger in watching this eclipse with your eyes or through a telescope," Fraknoi said.

Binoculars would be a neat way to watch the event, he said, because they could make some of the bigger craters stand out as the Earth's shadow begins to pass over the moon during the partial phase.

And watching the partial phase before totality should reveal something that the ancient Greeks discovered more than 2,000 years ago - that the Earth was round. So it wasn't Magellan whose voyage first showed that. It was Aristotle, who died in 322 B.C.

In eclipses of the moon, Aristotle wrote, the outline of the Earth's shadow is always curved, "and since it is the interposition of the earth that makes the eclipse, the form of this line will be caused by the form of the earth's surface, which is therefore spherical."

The lunar eclipse this year should be "really beautiful and like nothing you've ever seen before," said astronomer Ben Burress at the Chabot Space and Science Center high in the Oakland hills. "It's one of the longest lunar eclipses we've had."

The Chabot observatory is planning a big "Once in a Red Moon" all-night viewing party on its deck and in the planetarium with lunar-themed music. It will open at 10 o'clock tonight with hikes for the public and telescopes to see through. If the Bay Area's fog or clouds don't cooperate, the planetarium will show a simulation of the event.

Fred Espenak, an astronomer at NASA's Goddard Space Flight Center in Greenbelt, Md., has calculated the dates and times of past lunar eclipses from 2000 B.C. to the present, and on through to A.D. 3000. In that 5,000-year span, he said, there will have been 3,505 total eclipses of the moon, including 230 during the 21st century, and 4,213 partial eclipses, including 58 in this century.

Eclipses, of course, have long been harbingers of doom or evil in mythology, and lunar eclipses are no exception - mostly involving the moon swallowed up by gods or demons or other creatures.

According to some records, the Maya of Central America, for example, believed that a jaguar ate the moon and could devour people, too, while in ancient China it was a three-legged toad. To the Mongols it was a dragon named Alkha.

In Egypt in the time of the Pharaohs, lunar eclipses were bad omens indeed, because the moon was supposed to be the "ruler of the stars," and some ancient texts describe the entire sky as swallowing the moon during every eclipse.


KEY TERMS

Anomalistic month — The length of time required for the moon to travel around its orbit from its point of closest approach to Earth and back again.

Chromosphere — The bright red “ color sphere ” seen surrounding the sun as a narrow band when the photosphere is obscured.

Corona — A pearly white irregular shaped region surrounding the sun. It is visible only when the photosphere and chromosphere are obscured.

Node — The intersection of the lunar orbit with the plane of Earth ’ s orbit about the sun.

Nodical month — The length of time required for the moon to travel around its orbit from a particular node and back again.

Penumbra — From the Greek term meaning “ partially dark. ” Within the penumbral shadow part of the light source contributing to the eclipse will still be visible.

Photosphere — From the Greek term meaning “ light-sphere. ” This is the bright surface we associate with sunlight.

Saros — A cycle of eclipses spanning 18 years and 11 days first recorded by the Babylonians.

Synodic month — The time interval in which the phases of the moon repeat (from one full moon to the next), and averages 29.53 days.

Umbra — From the Greek meaning dark. Within the umbral shadow no light will be visible except in the case of Earth ’ s umbral shadow where some red sunlight may be refracted by the atmosphere of the Earth.

Earth and the sun while the line of nodes is aimed at the sun, the alignment between the sun, moon, and Earth will be perfect and a solar eclipse will occur. If the moon passes through the node lying beyond Earth when the line of nodes is properly oriented, we see a lunar eclipse.

Except for slow changes to the moon ’ s orbit, the line of nodes maintains an approximately fixed orientation in space as it is carried about the sun by Earth ’ s motion. Therefore, about twice a year the line of nodes is pointing straight at the sun and eclipses can occur. If the alignment is closely maintained during the two weeks between new moon and full moon, a solar eclipse will be followed by a lunar eclipse. A quick inspection of the table of pending eclipses shows that 20 of the 47 listed eclipses occur within two weeks of one another, indicating that these are times of close alignment of the line of nodes with the sun. A further inspection shows that these pairs occur about 20 days earlier each year indicating that the line of nodes is slowly moving westward across the sky opposite to the annual motion of the sun. At this rate it takes about

18.6 years for the nodes to complete a full circuit of the sky. Thus every 18-19 years eclipses will occur at about the same season of the year. After three of these seasonal cycles, or 56 years, the eclipses will occur on, or about, the same day. It is this long seasonal cycle that Gerald Hawkins associated with the 56 “ Aubry Holes ” at Stonehenge. He used this agreement to support his case that Stonehenge was used to predict eclipses and the Aubry Holes were used to keep track of the yearly passage of time between seasonal eclipses.

There are other cycles of eclipses that have been known since antiquity. It is a reasonable question to ask how long it will be before an eclipse will re-occur at the same place on Earth. The requirements for this to happen are relatively easy to establish. First, the moon must be at the same phase (i.e., either new or full depending on whether the eclipse in question is a solar or lunar eclipse). Secondly, the moon must be at the same place in its orbit with respect to the orbital node. Thirdly, the sun and moon must have the same distance from Earth for both eclipses. Finally, if the solar eclipses are to have similar paths across Earth, they must happen at the same time of the year. The first two conditions are required for an eclipse to happen at all. Meeting the third condition assures that the umbral shadow of the moon will reach Earth to the same extent for both eclipses. This means that the two eclipses will be of the same type (i.e., total or annular in the case of the sun). The last condition will be required for solar eclipses to be visible from the same location on Earth.

The interval between successive phases of the moon is called the synodic month and is 29.5306 days long. Due to the slow motion of the line of nodes across the sky, successive passages of a given node, called the nodal month, occur every 27.2122 days. Finally, successive intervals of closest approach to Earth (i.e., perigee passage) are known as the anomalistic month, which is 27.55455 days long. For the first three conditions to be met, the moon must have traversed an integral number of synodic, nodical, and anomalistic months in a nearly integral number of days. One can write these constraints as equations whose solutions are integers. However, such equations, called Diophantine equations, are notably difficult to solve in general. The ancient Babylonians found that 223 synodic months, 242 nodical months, and 239 anomalistic months all contained about 6, 585 1/3 days, which turns out to be just 11 days in excess of 18 years. They referred to the cycle as the Saros cycle, for it accurately predicted repeats of lunar eclipses of the same type and duration. However, the cycle missed being an integral number of days by about eight hours. Thus, solar eclipses would occur eight hours later after each Saros, which would be more than enough to move the path of totality away from any given site. After three such cycles, sometimes referred to as the Triple Saros, lasting 54 years and a month, even the same solar eclipses would repeat with fairly close paths of totality. Since the multiples of the various months do not exactly result in an integral number of days, the repetitions of the eclipses are not exactly the same, but they are close enough to verify the predictability and establish the cycles. The Babylonians were able to establish the Saros with some certainty. Their ability to do so supports Hawkins ’ notion that the people who built Stonehenge were also capable of establishing the seasonal eclipse cycle.

It is tempting to look for cycles of even longer duration in search of a set of synodic, nodical, and anomalistic months that would yield a more close number of days, but such a search would be fruitless. There are other subtle forces perturbing the orbit of the moon so that longer series of eclipses fail to repeat. Indeed, any series of lunar eclipses fails to repeat after about 50 Saros or about 870 years. Similar problems exist for solar eclipses.


The Moon does not emit its own light, shining instead by reflecting sunlight. Depending on the relative positions of the Earth, Sun and Moon, varying amounts of the lunar surface appear to be illuminated.

The Full Moon rises at sunset, transits the meridian at midnight and sets at sunrise. The Full Moon phase repeats every 29.531 days – one synodic month.

Lunar eclipses can only occur within a few days of the Full Moon, but they do not happen at every Full Moon. This is due to the 5.1 degree tilt of the Moon’s orbit around the Earth compared to the Earth’s orbit around the Sun. The intersection of these two orbits is the line of nodes, and lunar eclipses occur when this line is pointing towards the centre of the Moon.

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How bright is the full Earth during the lunar midnight? - Astronomy

What factors dictate if the moon is visible in the evening or morning (vs. at night)? My 15-month old loves to see the moon, but she is rarely awake at night so we always look for the moon early in the morning and in the evenings. I'm just curious why it is sometimes visible and sometimes not. (Obviously cloud cover is a factor, but outside of that.) Background: I am a curious person with a very curious daughter. Thanks so much.

When the moon is visible depends where it is in its orbit. Look at the following image:

The Earth turns counter clockwise and the Moon follows the black circle counter clockwise. The labels AM, Noon, PM, Midnight indicate your location on the Earth during the day. The labels New, 1st Quarter, Full and 3rd Quarter label the positions of the Moon along its orbit. The Sun is on the left side.

As you can see the Moon will be visible in the evening (PM side of the Earth) starting a few days past new moon, during first quarter until a few days before full moon. It will be visible in the morning (AM side of the Earth) starting at full moon, during third quarter until a few days before new moon. The Moon will not be visible for a few days around new moon because the sunlit side of the Moon is facing away from Earth, towards the Sun. Consult your calendar for the phases of the Moon.

A fun thing to do is to make a picture of the Earth and the Sun with the path of the Moon like the image above and have a Moon cutout to move around the Earth. You stick the cutout Moon onto the orbit and can move it every few days to the Moon's current position. This will help you (and maybe later your child) to know when to go out and see the Moon. This "Moon Clock" can also be used to understand the phases of the Moon by keeping the bright side of the Moon facing the Sun.

About the Author

Marc Berthoud

Marc worked on the FORCAST camera for the SOFIA airborne observatory. He now is a staff astronomer at the Yerkes Observatory.


How bright is the full Earth during the lunar midnight? - Astronomy


The best image I was able to get of the total lunar eclipse of Apr 4, 2015 using a Kindle Fire to take a 4-power image of the Moon. The entire Moon was in the umbra of the Earth for a little less than 5 minutes, hence the term "total" eclipse, but it was just barely in the umbra (which is why the total phase lasted less than 5 minutes), so the northern part of the Moon was just barely covered by our shadow, and sunlight shining through the ring of air surrounding the body of the Earth lit up that part much more than the regions deeper in the shadow, making them look much darker. In fact, the southernmost part was much darker than in the image taken by the tablet. Next time round I'll use my 12-power digital camera, but it had been in storage due to our last remodeling project, and the battery had run down. :-(

The Shadow of the Earth
As shown in the diagram below, two lines can be drawn from the bottom of the Sun past the Earth, to define a region where the Earth blocks any view of the bottom of the Sun and similarly, two lines can be drawn from the top of the Sun past the Earth, to define a region where the Earth blocks any view of the top of the Sun. Where those overlap on the night side of the Earth is the Earth's umbra (Latin for shadow), a region where neither the top nor the bottom of the Sun can be seen (nor of course, any part in between). Where they do not overlap is the Earth's penumbra (Latin for partial shadow), a region where part of the Sun is visible and part of it is blocked from view by the Earth. In the upper part of the penumbra the Earth is in front of the bottom of the Sun, but an observer could look over the top of the Earth and still see the top of the Sun while in the lower part of the penumbra the Earth is in front of the top of the Sun, but an observer could look under the bottom of the Earth and still see the bottom of the Sun.

The shadow of the Earth
(not to scale objects are shown larger and closer together than in reality)


Imaging the Lunar Eclipse

I was pleasantly surprised when the clouds rolled out and the weather turned out to be favorable for the total lunar eclipse last night! After work, I went home for a quick nap and put on layers and layers of clothing to help me brave the cold on the eve of the winter solstice. Friends and coworkers told me I was crazy to come back to work at midnight for the eclipse, especially with the temperatures predicted to be in the 20s. But the clear skies, which have been hard to come by so far this month, were more than this astronomy educator could resist. So I met fellow astronomy educator Erin Braswell at National Air and Space Museum’s Public Observatory at 1 a.m. to begin preparations for a night of observing and imaging the lunar eclipse. Our goal was twofold: to experience the eclipse for ourselves, and to capture it to share with our colleagues and visitors. The 16-inch Boller and Chivens which is the main telescope at the Public Observatory, is a very high-powered telescope, great for seeing the tiny details of the Moon’s craters and other features. However, it magnifies too much to see the entire Moon in one shot so isn’t a great choice for eclipse viewing or imaging. Instead, we used the Public Observatory’s TeleVue-85 refracting telescope along with a Lumenera 2-0 color camera and a Lumenera 2-2 monochromatic camera.

Lunar eclipse seen from The National Air and Space Museum's Public Observatory on the morning of December 21, 2010.

Images by Erin Braswell and Katie Moore.

The photograph, above, will give you a quick snapshot of our experience. If you observed the eclipse, you might notice that the photo does not do it justice. The human eye is much more capable of seeing a range of details and colors on the bright and the eclipsed portions of the Moon, while the camera can only detect one part at a time. In reality, the “dark” portion of the Moon is still easily visible to the naked eye, although noticeably fainter than normal. Our cameras only capture, the brighter, uneclipsed portions of the Moon during the partial phases. During totality, they capture the fainter, eclipsed Moon. In addition, the color is more vivid to the naked eye, during totality. As predicted, during totality, the Moon was not uniform in brightness - it was slightly dimmer at the bottom, which was closer to the center of the Earth’s shadow. Also, since the Moon didn’t pass through the middle of the Earth’s umbra, the eclipse doesn’t progress straight across the Moon. The things I most enjoy about lunar eclipses are seeing such a familiar object as the Moon take on an unusual appearance, and thinking about how our closest celestial neighbors are arranged to make it happen. The Sun’s rays usually illuminate the Moon directly, but during a lunar eclipse, the Earth gets in the way. This causes the partial stages of the eclipse. Here you can rediscover that the Earth is a spherical object when watching the curved shadow of the Earth moving across the Moon! Then, during totality, the Moon is illuminated by sunlight that seeps through the Earth’s atmosphere, giving it the fainter, reddish glow. You can almost feel the heavens line up! Did you photograph the total lunar eclipse? We’d love to see the results! Upload your images to the Public Observatory Project’s group page on Flickr.


Midnight Delight: Total Lunar Eclipse

Total Lunar Eclipse Dec 20/21 2010
The Moon and the Earth have a very special relationship in the Cosmos. The Moon is close enough to us to tug our oceans into tidal swells, and even to make you (very slightly) lighter when it's overhead. You can even "touch" the Moon, electromagnetically, by aiming a flashlight at it and pressing the button: about a second after you do, the photons you launch physically contact the soil and rock on the Moon's surface (and the way a flashlight beam spreads out, you don't even need good aim). And of course the Moon is the only place in the Universe we've personally visited.

One of the most striking and beautiful examples of the Earth-Moon relationship takes place during a total lunar eclipse, when the Moon passes through the Earth's shadow, transforming in a couple of hours from the stark brilliance of the Full Moon to the dark ruby-hued wonder of "umbral occlusion"&mdashor totality.

Monday evening, December 20th, starting at about 9:30 PM, the Moon will begin to enter the Earth's partial, or "penumbral," shadow. Around 10:30, it begins to enter the umbra (full shadow), and by 11:40 will be completely engulfed: "totality." Totality will last until 12:53 AM Tuesday morning, when the Moon begins to leave the umbra.

While the extended weather forecast at the moment doesn't look favorable for the SF Bay Area, there are always freak changes in weather to hope for. Also, we'll be having a Lunar Eclipse celebration at Chabot Space & Science Center, rain or moonshine, which will be a lot of fun: Lunar Labs, planetarium shows, sci-fi movie reels, and every Moon-related song we could find&mdashhope to see you there!

Though a total lunar eclipse is a rare event to see, this one is rarer still--not the least reason being that for the Western US it will be one of the highest lunar eclipses you can see, with the Moon reaching its apex for the night over 75 degrees from the horizon (practically overhead) close to mid-totality. For our latitudes in the Bay Area, the Moon can't get much higher than that. So, we get High Moon when the eclipse is at its best (weather permitting).

What makes this eclipse rare among the rare is the fact that the Moon is crossing several important features in the sky simultaneously. First, it's crossing the Ecliptic, the path of the Sun's apparent motion over the course of a year, cutting through the 12 constellations of the Zodiac. In essence, the Ecliptic is the projection of Earth's orbital plane onto the sky. Is it a coincidence that the Moon will be crossing the Ecliptic during this eclipse? Actually&hellipnot at all. By virtue of the geometry of a lunar eclipse, the Moon must be on the Ecliptic in order to pass through Earth's shadow, since the Earth's shadow, cast by the Sun's light, always runs along Earth's orbital plane, and so too the Ecliptic.

Another line is crossed during this eclipse because it happens on Winter Solstice. On this day, the Sun is located in Sagittarius, and so the Earth's shadow is cast toward the opposite point on the sky, in Taurus. Halfway around the circle of the Ecliptic from the Winter Solstice point you find the other solstice point, the spot on the Ecliptic where the Sun is located at Summer Solstice.

The Moon will also be crossing the Galactic Equator: the line representing the plane of the Milky Way Galaxy. This alignment is a bit more tangible than those with the Ecliptic and the Solstice point since the Milky Way is a visible sky feature&mdashat least in areas not impacted by urban light pollution. If you live in a place where you can normally see the Milky Way on a dark night, you have an extra wonder to marvel at during this eclipse: when the bright Full Moon enters totality and goes dark, the subtle light of our galaxy will be revealed, with the Moon set like a darkling gem in a diamond bracelet&hellip.

Well, we can only hope for clear skies&mdashbut in either event, come up to Chabot and celebrate with us this midnight delight&hellip.


Watch the video: Σελήνη (June 2022).


Comments:

  1. Arashilar

    something with me personal messages do not go out, error ....

  2. Disho

    I didn't quite understand what you meant by that.

  3. Nikorisar

    Do not be upset! More fun!



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