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techstepgenr8tion
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05 Mar 2013, 7:38 am

http://news.yahoo.com/nasa-spacecraft-p ... 29899.html

Look at the top photo of Venus from Saturn in this article. Something just seems bizarre about it, meaning it looks like it has two light-sources and an incomplete ring ecliptic to where it largely looks like the whole thing is circling behind the planet. There's no possible way that Cassini could 'shine a light' on Saturn and cast a drop shadow that I know of (unless they've got a billion lumen bulb on board that we'd see from Earth). I'm not saying its a hoax, I'm just saying that I'm stumped on the lighting.



naturalplastic
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05 Mar 2013, 8:27 am

I dont understand the picture either.
The article doesnt really explain to the reader what they are looking at.

The subject of the article: the faint dots that are Venus showing through saturn's rings make sense. But the picture as a whole does not make sense.

The planet seems to be outlined in an artificially bold bright line that has to be an artifact put in the picture- not something thats in the picture ( im thinking it might be some technique akin to that used when astronomers artificially block the sun in order to photograph stars in the sky parts near the sun). That line appears in the small lower picture as well, and is described in the article as 'the limb of the planet"( didnt know that planets had arms and legs).

In the top picture (a) the planet seems to be in front of its rings rather than surrounded by them. And it does seemed to be casting a shadow on its rings(the black wedged knotched out of the rings in the upper right of the picture. If you were looking at saturn from the sunward side you would expect it to cast a shadow on its rings as they go behind the planet. But it was taken from the dark side of the planet ( the only way you could position venus behind saturn's rings would be if you shot saturns rings from the side away from the sun).

Beats me.



techstepgenr8tion
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05 Mar 2013, 8:36 am

naturalplastic wrote:
The planet seems to be outlined in an artificially bold bright line that has to be an artifact put in the picture- not something thats in the picture.

I've seen that outline before, just that its usually been the probe shooting from a midnight position.


naturalplastic wrote:
In the top picture (a) the planet seems to be in front of its rings rather than surrounded by them. And it does seemed to be casting a shadow on its rings(the black wedged knotched out of the rings in the upper right of the picture. If you were looking at saturn from the sunward side you would expect it to cast a shadow on its rings as they go behind the planet. But it was taken from the dark side of the planet ( the only way you could position venus behind saturn's rings would be if you shot saturns rings from the side away from the sun).

Yeah, all of the above to add as well that the rings that seem to be going across the face of the picture look like they're partially chopped. Not impossible that if a ring portion is pale enough that it won't show up against the planet but it seems disproportionate in dark/light with reference to what you see past that near-noon drop shadow at the top.



Tollorin
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05 Mar 2013, 11:09 am

I think it's the light reflected by the rings.


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naturalplastic
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05 Mar 2013, 3:32 pm

Tollorin wrote:
I think it's the light reflected by the rings.


What is?



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05 Mar 2013, 3:52 pm

To "shine a light" on something is to illuminate or, in the metaphorical case, reveal it.

The "limb" of a moon, planet, or star is it's circumferential edge.

The seeming transparency of Saturn in the upper right corner is either a double-reflection in the camera's lenses, or an artifact of the image's capture and processing. Working with video "frame grabbers" every day, I know how easy it is to obtain such images if the synchronization isn't exactly perfect


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techstepgenr8tion
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05 Mar 2013, 5:41 pm

Fnord wrote:
The seeming transparency of Saturn in the upper right corner is either a double-reflection in the camera's lenses, or an artifact of the image's capture and processing. Working with video "frame grabbers" every day, I know how easy it is to obtain such images if the synchronization isn't exactly perfect

The problem is I can't even judge which part of the ecliptic should be going across the side of the planet we're viewing from the picture itself - ie. its a small enough chunk that its difficult to determine if they're above or below the ring. That's what makes interpreting the actual positioning of the ring incredibly tough.



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05 Mar 2013, 5:58 pm

Compare and contrast - Cassini's view of Saturn eclipsing the Sun. Check out the "Exaggerated Color Contrast" image (click on it)
http://photojournal.jpl.nasa.gov/catalog/PIA08329


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techstepgenr8tion
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05 Mar 2013, 6:10 pm

I've seen that photo several times, part of why I'm not really as concerned about the hard outline of light around the planet. I'm not sure if that's solar lensing or simply qualities of that layer of Saturn's atmosphere. What I was really more interested in is seeing the ring go behind the planet in the lower part and having a drop shadow covering it on the top part along with only a partial presentation of the ring. That just looked....strange.



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05 Mar 2013, 6:28 pm

Oh, the shadow...
Cassini is looking "up" at Saturn with the Sun positioned lower down and behind Saturn, therefore the dark shadow at the top is caused by Saturn blocking the light as it falls onto the rings in the foreground.
From this viewpoint the rings are hidden by Saturn at the bottom of the picture, and are between Cassini and Saturn at the top so with the light source being below and behind Saturn, the shadow is cast upwards onto the "underside" of the rings.
Due to the cropping it's only just possible in this image to see the rings at the top passing between Cassini and Saturn - that's visible almost at the end of the bright white line.


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techstepgenr8tion
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05 Mar 2013, 6:43 pm

I *think* I might know what you're getting at.

Its a really strange visual case though in that the drop-shadow seems to be behind it but it sounds like your suggesting that the transparency of the rings are just creating an optical illusion to that extent, ie. that the drop shadow in the upper right is really closer to rather than farther from the camera in respect to the planet.



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05 Mar 2013, 6:48 pm

techstepgenr8tion wrote:
the drop shadow in the upper right is really closer to rather than farther from the camera in respect to the planet.
Yep, that's it exactly.


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ruveyn
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06 Mar 2013, 7:00 am

naturalplastic wrote:
I dont understand the picture either.
The article doesnt really explain to the reader what they are looking at.

The subject of the article: the faint dots that are Venus showing through saturn's rings make sense. But the picture as a whole does not make sense.

.


Singular. Only one bright dot.

Light is diffused in the outer layer of Saturn gas.

ruveyn



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06 Mar 2013, 11:21 am

Personally, I think the light is in relation to the camera rather than the planet.

On the first picture you can see the curve of white light but you can also see the curve on Saturn just beside that. The article explains it was in Saturns shadow when the pics were taken and the fact the rings continue is more to do with reflection bouncing off more than one mirror, rather than the planet itself. Hence why you have the rings in the reflection rather than a shot of the camera.

Space cameras use mirrors and lights so it just appears to be the reflection from the camera itself rather than anything to do with Saturn. It's evident again on the 2nd pic, though due to the rotation and distance, it does appear that the light is around Saturn. That one I think is just coincidence but makes for an amazing shot.



naturalplastic
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06 Mar 2013, 3:01 pm

ruveyn wrote:
naturalplastic wrote:
I dont understand the picture either.
The article doesnt really explain to the reader what they are looking at.

The subject of the article: the faint dots that are Venus showing through saturn's rings make sense. But the picture as a whole does not make sense.

.


Singular. Only one bright dot.

Light is diffused in the outer layer of Saturn gas.

ruveyn


I meant the one dot each in each of the two pictures. And then focused on the talking about the peripherial parts of the one big upper picture being distorted, but forgot to specify that I switched to talking about that one picture. Sorry if i confused.