APOD: 3D 67P (2017 Mar 31)

[APOD Robot]

3D 67P

Explanation: Get out your red/cyan glasses and gaze across the surface of Churyumov-Gerasimenko, aka Comet 67P. The stereo anaglyph was created by combining two images from the Rosetta spacecraft's narrow angle OSIRIS camera taken on September 22, 2014. Stark and jagged, the 3D landscape is found along the Seth region of the comet's double-lobed nucleus. It spans about 985 x 820 meters, pocked by circular ridges, depressions, and flattened areas strewn with boulders and debris. The large steep-walled circular pit in the foreground is 180 meters in diameter. Rosetta's mission to the comet ended in September 2016 when the spacecraft was commanded to a controlled impact with the comet's surface.

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[Chris Peterson]

Crossed-eye stereo pair for those who prefer a more natural view.

[DL MARTIN]

Did the photos just get here, now?

[heehaw]

Crossed-eye stereo pair for those who prefer a more natural view.

APOD-67P-Seth-cross.jpg

Thanks so much Chris! Two questions: is the vertical scale (from the surface) true, or is it exaggerated? and, is the round deep hole on the right a spout ejection hole?

[dromeuf]

Download the full resolution on the computer. Zooming the image with the mouse wheel is a real sensation, dive, fly over these reliefs ...

[Chris Peterson]

Crossed-eye stereo pair for those who prefer a more natural view.
APOD-67P-Seth-cross.jpg

Thanks so much Chris! Two questions: is the vertical scale (from the surface) true, or is it exaggerated? and, is the round deep hole on the right a spout ejection hole?

3D images of nearly all astronomical objects appear exaggerated, since if the pairs are only separated by the width of our eyes we'd see no 3D effect at all. But these are made from ordinary images, not reconstructed spatial data, so no axis is exaggerated with respect to any other.

[neufer]

The Hunting of the Snark
By Lewis Carroll

Fit the Fifth: The Beaver's Lesson

[b][i][color=#0000FF]They sought it with thimbles, they sought it with care; They pursued it with forks and hope; They threatened its life with a railway-share; They charmed it with smiles and soap.[/color][/i][/b]

---

Then the Butcher contrived an ingenious plan
For making a separate sally;
And had fixed on a spot unfrequented by man,
A dismal and desolate valley.

But the very same plan to the Beaver occurred:
It had chosen the very same place:
Yet neither betrayed, by a sign or a word,
The disgust that appeared in his face.

Each thought he was thinking of nothing but "Snark"
And the glorious work of the day;
And each tried to pretend that he did not remark
That the other was going that way.

But the valley grew narrow and narrower still,
And the evening got darker and colder,
Till (merely from nervousness, not from good will)
They marched along shoulder to shoulder.

Then a scream, shrill and high, rent the shuddering sky,
And they knew that some danger was near:
The Beaver turned pale to the tip of its tail,
And even the Butcher felt queer.

He thought of his childhood, left far far behind—
That blissful and innocent state—
The sound so exactly recalled to his mind
A pencil that squeaks on a slate!

"'Tis the voice of the Jubjub!" he suddenly cried.
(This man, that they used to call "Dunce.")
"As the Bellman would tell you," he added with pride,
"I have uttered that sentiment once.

"'Tis the note of the Jubjub! Keep count, I entreat;
You will find I have told it you twice.
Tis the song of the Jubjub! The proof is complete,
If only I've stated it thrice."

The Beaver had counted with scrupulous care,
Attending to every word:
But it fairly lost heart, and outgrabe in despair,
When the third repetition occurred.

It felt that, in spite of all possible pains,
It had somehow contrived to lose count,
And the only thing now was to rack its poor brains
By reckoning up the amount.

"Two added to one—if that could but be done,"
It said, "with one's fingers and thumbs!"
Recollecting with tears how, in earlier years,
It had taken no pains with its sums.

"The thing can be done," said the Butcher, "I think.
The thing must be done, I am sure.
The thing shall be done! Bring me paper and ink,
The best there is time to procure."

The Beaver brought paper, portfolio, pens,
And ink in unfailing supplies:
While strange creepy creatures came out of their dens,
And watched them with wondering eyes.

So engrossed was the Butcher, he heeded them not,
As he wrote with a pen in each hand,
And explained all the while in a popular style
Which the Beaver could well understand.

"Taking Three as the subject to reason about—
A convenient number to state—
We add Seven, and Ten, and then multiply out
By One Thousand diminished by Eight.

"The result we proceed to divide, as you see,
By Nine Hundred and Ninety and Two:
Then subtract Seventeen, and the answer must be
Exactly and perfectly true.

"The method employed I would gladly explain,
While I have it so clear in my head,
If I had but the time and you had but the brain—
But much yet remains to be said.

"In one moment I've seen what has hitherto been
Enveloped in absolute mystery,
And without extra charge I will give you at large
A Lesson in Natural History."

[dromeuf]

and, is the round deep hole on the right a spout ejection hole?

Figure 4: Pit formation mechanism by sinkhole collapse.
http://www.nature.com/nature/journal/v5 ... 64_F4.html

[MarkBour]

Be wary of such pits. Exogorths like making their homes in them. (Though I believe they prefer asteroids to comets.)

[moontrail]

In my opinion, the vertical axis appear exaggerated, or the horizontal axis appear reduced, or the equivalent mix of both, in the same proportion as the distance between the places where the two photographs were taken to the distance between our eyes.

Crossed-eye stereo pair for those who prefer a more natural view.
APOD-67P-Seth-cross.jpg

Thanks so much Chris! Two questions: is the vertical scale (from the surface) true, or is it exaggerated? and, is the round deep hole on the right a spout ejection hole?

3D images of nearly all astronomical objects appear exaggerated, since if the pairs are only separated by the width of our eyes we'd see no 3D effect at all. But these are made from ordinary images, not reconstructed spatial data, so no axis is exaggerated with respect to any other.

[moontrail]

In my opinion, the vertical axis appear exaggerated, or the horizontal axis appear reduced, or the equivalent mix of both, in the same proportion as the distance between the places where the two photographs were taken to the distance between our eyes.

Thanks so much Chris! Two questions: is the vertical scale (from the surface) true, or is it exaggerated? and, is the round deep hole on the right a spout ejection hole?

3D images of nearly all astronomical objects appear exaggerated, since if the pairs are only separated by the width of our eyes we'd see no 3D effect at all. But these are made from ordinary images, not reconstructed spatial data, so no axis is exaggerated with respect to any other.

What we see in this 3D "images" is a reality’s scale model (Scale: distance between eyes/distance between places where camera took the two images) that only coincides with the object reduced image for plain objects. The “image” vertical scale will coincide with the horizontal only if the distance from our eyes to the screen keeps the Scale with the distance from cameras to object. The "image" vertical scale will result enhanced if we see the screen from a wider distance or reduced in other case.

[dromeuf]

In this anaglyphe, the near object is about 27472 meters to the ROSETTA spacecraft. The far object is about 29138 meters. The depth is about 1666 meters. The stereo hyper-base is about 1944 meters (distance between two spacecraft positions to take this couple, in two time). The parallax to the near object is about 3.9°-4.0° (disparity of infinite homologue points 1/14.1). This value is acceptable by the brain but this is a higher limit for displaying on a very large computer screen. We commonly use 2°, 3° for computer screen projection (1/30, 1/20) for binocular compatibility.

There is an ideal position to observe any stereoscopic document. There is only one ortho-stereoscopic position (only one spectator in a movie theater). I explain this in this web-article :
http://www.david-romeuf.fr/3D/Anaglyphe ... olume.html


I explain ideal comfort formulae for observer in this web-article (in french, tranlate with google) :
http://www.david-romeuf.fr/3D/CalculsSt ... aphie.html

Influence of the shot parallax for an identical display dimension. left to right 3.4° - 5.7° and 8.5°. The comfort limit deformation is about > 5°

Full res : http://www.david-romeuf.fr/3D/CalculsSt ... %20rec.png