APOD: Lunar Shadow Transit (2016 Mar 11)

Comments and questions about the APOD on the main view screen.
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APOD: Lunar Shadow Transit (2016 Mar 11)

Post by APOD Robot » Fri Mar 11, 2016 5:06 am

Image Lunar Shadow Transit

Explanation: This snapshot from deep space captures planet Earth on March 9. The shadow of its large moon is falling on the planet's sunlit hemisphere. Tracking toward the east (left to right) across the ocean-covered world the moon shadow moved quickly in the direction of the planet's rotation. Of course, denizens of Earth located close to the shadow track centerline saw this lunar shadow transit as a brief, total eclipse of the Sun. From a spacebased perspective between Earth and Sun, the view of this shadow transit was provided by the Deep Space Climate Observatory (DSCOVR) spacecraft's Earth Polychromatic Imaging Camera (EPIC).

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by revloren » Fri Mar 11, 2016 5:27 am

Was it just luck that DSCOVR was just in the right place to capture a 'full earth' during the eclipse?

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by Nitpicker » Fri Mar 11, 2016 6:25 am

DSCOVR is in a small orbit around the Earth-Sun Lagrange point 1 (L1), which is always between the Sun and Earth and about four times further from Earth than the Moon.

But I'm sure there was a bit of luck involved to get DSCOVR funded, built and launched into that orbit, not to mention the luck required for the creation of the Earth and Moon around the Sun.

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by Ann » Fri Mar 11, 2016 6:27 am

APOD Robot wrote very early in the morning on March 10:
Tomorrow's picture: East of Java
Look, someone spilled their Java in the ocean!

Ann
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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by Chris Peterson » Fri Mar 11, 2016 6:30 am

revloren wrote:Was it just luck that DSCOVR was just in the right place to capture a 'full earth' during the eclipse?
No. It's always very near the Earth-Sun L1 point- that is, on a line between the Sun and Earth. All it ever sees is a full Earth. And had the eclipse followed a slightly different path, it might even have captured the Moon in the same frame, since DSCOVR is quite a bit farther away than the Moon.
Chris

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by Boomer12k » Fri Mar 11, 2016 6:53 am

Awesome...to see it from space.... Good thing it is not a MAGNIFYING GLASS.... :shock:

Amazing, it is about or bigger than Australia....Crickies, mate....

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by gerden » Fri Mar 11, 2016 8:33 am

Can anyone tell me, why we don't see the moon in the photograph?
As e.g. compared to here:
http://www.nasa.gov/feature/goddard/fro ... e-of-earth

Thanks in advance

Simon

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by Boomer12k » Fri Mar 11, 2016 11:22 am

gerden wrote:Can anyone tell me, why we don't see the moon in the photograph?
As e.g. compared to here:
http://www.nasa.gov/feature/goddard/fro ... e-of-earth

Thanks in advance

Simon

The Moon is still off to the left...and it is not an animation...

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by Beyond » Fri Mar 11, 2016 12:16 pm

Ann wrote:
APOD Robot wrote very early in the morning on March 10:
Tomorrow's picture: East of Java
Look, someone spilled their Java in the ocean!

Ann
Good one, Ann. :clap: Yes, someone is mooning over their spilled Java.
To find the Truth, you must go Beyond.

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by neufer » Fri Mar 11, 2016 1:15 pm

gerden wrote:
Can anyone tell me, why we don't see the moon in the photograph?
As e.g. compared to here:
http://www.nasa.gov/feature/goddard/fro ... e-of-earth
At any given time the DSCOVR spacecraft position varies up to 15 degrees off from the sun-Earth line so during a solar eclipse it seldom sees the moon near the ~ half degree wide Earth.
http://www.nesdis.noaa.gov/DSCOVR/ wrote:
<<The DSCOVR spacecraft orbits around the L1 Lagrange point directly between Earth and the sun. This orbit keeps the spacecraft near the L1 point and requires only occasional small maneuvers, but its orbit can vary from 4 to 15 degrees away from the sun-Earth line over several years.>>
Art Neuendorffer

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by neufer » Fri Mar 11, 2016 1:31 pm

Ann wrote:
APOD Robot wrote:
very early in the morning on March 10:
Tomorrow's picture: East of Java
Look, someone spilled their Java in the ocean!
  • So we Sea. (Must fix that shaky Sunda Shelf some day.)
https://en.wikipedia.org/wiki/Java_Sea wrote:

<<The Java Sea is a large shallow sea on the Sunda Shelf formed as sea levels rose at the end of the last ice age. The Java Sea lies between the Indonesian islands of Borneo to the north, Java to the south, Sumatra to the west, and Sulawesi to the east. Karimata Strait to its northwest links it to the South China Sea. The sea measures about 1,500 km east-west by 420 km north-south and occupies a total surface area of 433,000 square km. It covers the southern section of the 1,790,000-square-km Sunda Shelf. A shallow sea, it has a mean depth of 46 metres. The almost uniform flatness of the sea bottom and the presence of drainage channels (traceable to the mouths of island rivers) indicate that the Sunda Shelf was once a stable, dry, low-relief land area (peneplain) above which were left standing a few monadnocks (granite hills that by virtue of their resistance to erosion form the present islands). The southern section of the seafloor has long been recognized as geologically similar to northern Java, where oil fields occur and extend under the sea. Prospects are also favourable for oil fields in the waters off southeast Kalimantan. As the site of successful exploration for petroleum and natural gas, the Java Sea has become the basis of Indonesia’s export program.>>
Art Neuendorffer

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by MarkBour » Fri Mar 11, 2016 6:48 pm

This APOD makes a beautiful pair with yesterday's. I don't suppose I can match up a cloud from yesterday's APOD with a cloud in today's APOD. But there certainly is a resemblance, and I believe the timing of the two photos must have been fairly close.

In today's image, the lunar shadow has not yet covered the Sun's reflection point off of the Pacific, so we've got dark and light together. DSCOVR is soooo cool!
Mark Goldfain

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by alcor » Fri Mar 11, 2016 7:18 pm

Beyond wrote:
Ann wrote:
APOD Robot wrote very early in the morning on March 10:
Tomorrow's picture: East of Java
Look, someone spilled their Java in the ocean!

Ann
Good one, Ann. :clap: Yes, someone is mooning over their spilled Java.
And after they spilled it they sang about their loss https://www.youtube.com/watch?v=iP6IUqrFHjw 8-)

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by BobStein-VisiBone » Fri Mar 11, 2016 7:46 pm

Boomer12k wrote:
gerden wrote:Can anyone tell me, why we don't see the moon in the photograph?
As e.g. compared to here:
http://www.nasa.gov/feature/goddard/fro ... e-of-earth

Thanks in advance

Simon

The Moon is still off to the left...and it is not an animation...

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I wondered the same thing, Gerden.

Boomer, I first thought the moon must be to the left since its shadow is left of the sun's reflection point, the bright spot near the center. But now I think the moon was actually above and right of the Earth, and here's why. If you look at the edge of the Earth in this photo, it's fuzzy between about the 5 and 8 oclock positions, and sharp everywhere else. This must mean that the DSCOVR satellite was a little off from being directly between Earth and Sun. So a line between Earth and Sun centers in this photo would exit at about the 1 or 2 oclock direction. And the moon must be very near that.

I wish they had zoomed out a little to catch the moon in this picture. But I'm definitely not complaining.

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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by alter-ego » Fri Mar 11, 2016 11:33 pm

BobStein-VisiBone wrote: ...
Boomer, I first thought the moon must be to the left since its shadow is left of the sun's reflection point, the bright spot near the center. But now I think the moon was actually above and right of the Earth...
That is correct; the Moon/Sun axis is above and to the right wrt DSCOVR.
At the time of the image, and as viewed from Earth, the line connecting the Earth and Sun is high (5.5°) and to left (3.2°) of DSCOVR. So the Sun - Earth - DSCOVR angle ~6.5°. Keeping the Earth centered in a wider-field image, DSCOVR's FoV would need to be ~6x wider to include the Moon.

Edit:
Relative to DSCOVR, I've recreated the eclipse circumstances in Stellarium for this APOD. The screenshot below (not a composite) shows both the Earth and Moon as viewed from DSCOVR at the nominal time of the APOD.
Earth & Moon from DSCOVR.JPG
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Last edited by alter-ego on Sat Mar 12, 2016 10:18 pm, edited 1 time in total.
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Re: APOD: Lunar Shadow Transit (2016 Mar 11)

Post by BMAONE23 » Sat Mar 12, 2016 2:23 am

Chris Peterson wrote:
revloren wrote:Was it just luck that DSCOVR was just in the right place to capture a 'full earth' during the eclipse?
No. It's always very near the Earth-Sun L1 point- that is, on a line between the Sun and Earth. All it ever sees is a full Earth. And had the eclipse followed a slightly different path, it might even have captured the Moon in the same frame, since DSCOVR is quite a bit farther away than the Moon.
Like this
https://m.youtube.com/watch?v=DMdhQsHbWTs