Nasa - Space Lighting Technique

[CustomMinds]

This is a bit completely random. I was looking at cnn.com this morning and ran across an article about an object hitting Saturn. In their photos they posted the following image. The black dot is supposed to be a shadow cast by Saturn's moon Io. I believe to the lower right of the shadow is the actual moon.

The question I have is... is this dark circle fabricated? (modified by photoshop or something). Or is the shadow actually Io (I do not know why it would not reflect any light when this angle of Saturn does). The shadow just looks fake to me.

Here's the image. Let me know your thoughts.

http://i2.cdn.turner.com/cnn/2009/TECH/space/07/21/jupiter.nasa.meteor.scar/art.jupiter.gi.jpg
http://i2.cdn.turner.com/cnn/2009/TECH/space/07/21/jupiter.nasa.meteor.scar/art.jupiter.gi.jpg

[alt4852]

looks like jupiter to me. ;)

[CustomMinds]

-alt4852

well at least you didn't post a 'Uranus' comment. ;-)


edit (after sorarse) - woops... didn't even pay attention to that. Thanks alt. Thought you were just making a joke about the majority of the photo being Jupiter.

[Sorarse]

I can see a moon and the shadow it's casting, but as alt4852 said, that's Jupiter, not Saturn.

[CustomMinds]

oh .. lol. okay...

i got too caught up looking at Io's shadow. my bad people.

now that we have established it is Jupiter... please find and replace the initial post from Saturn to Jupiter and address the initial question.

thanks

[CustomMinds]

Here is my reasoning...

a) the planet should reflect enough light to the back side of IO to prevent the strong black seen in the photo.

b) Also, since it is a gas planet, their should also be light diffusion once the light hits the gaseous surface. (diffusing the light around the edges.)

I guess no one has reason to modify the image... but still the black dot just doesn't look real.

[Photon Phil]

Gotta be enhanced in some way.

Jupiter the name intrigues me, especially on lenses.

The thought of the place terrifies me. Perhaps 2010 the movie did that to me.

[alt4852]

i'm pretty sure it's real. i've seen shadow casts on planets from moons before and they all look like that.

http://www.hour25online.com/pix/saturn-rings-gray-02a.jpg

that's saturn casting a shadow on it's own rings. you can see how solid the deep black shadow is of a gaseous planet on it's own ice and dust rings. i'm sure io would cause a similarly dark and localized shadow on jupiter.

[Photon Phil]

Wow, but by that far out I'd suppose the sun is like a 580ex at a good distance.

[CustomMinds]

well... First off, I am of course wrong... But for arguments sake I will say the following...

A counter to this, behind the rings of the Saturn Photo, there is dark 'space'. you can also visibly see Saturn's dark side from the photo. I hope I get this right, but Jupiter comes before Saturn in relation to our suns light source.

on the photo i displayed, it is as if their is a hole straight through Jupiter.

I think, if anything, it should be a shade of gray rather than lacking all light.





i'm pretty sure it's real. i've seen shadow casts on planets from moons before and they all look like that.

http://www.hour25online.com/pix/saturn-rings-gray-02a.jpg

that's saturn casting a shadow on it's own rings. you can see how solid the deep black shadow is of a gaseous planet on it's own ice and dust rings. i'm sure io would cause a similarly dark and localized shadow on jupiter.

[CustomMinds]

Wow, but by that far out I'd suppose the sun is like a 580ex at a good distance.
heh - is that a stab at canon?

;-)

[Nighthound]

Here is my reasoning...

a) the planet should reflect enough light to the back side of IO to prevent the strong black seen in the photo.

b) Also, since it is a gas planet, their should also be light diffusion once the light hits the gaseous surface. (diffusing the light around the edges.)

I guess no one has reason to modify the image... but still the black dot just doesn't look real.

Reflected light that is coming from Jupiter would not effect the illumination within Io's shadow itself. To do so, Io would need to be even closer to the planet's cloud tops to send substantial light back into its own shadow. The hardness of the shadow's edge is determined by the intensity of the light source and the distance in which it is cast. Even though this image displays amazing detail it is still a distant image of an enormous region which has a compression effect on the visual detail of the shadow's edge. A highly magnified image of the shadow would likely show a much softer edge.

[cruiser]

Possibly another thing to look at would be the contrast adjustments done to the photo. The contrast of the photo could be changed to show the shadow a more grey tone but then that would also brighten the rest of the shot reducing the detail in all other features.

[Sorarse]

I think, if anything, it should be a shade of gray rather than lacking all light.

How grey do parts of our own moon look when not in direct sunlight? It looks pretty black to me, despite being a lot closer to the sun than either Jupiter or Saturn.

[factorgrimm]

The shadowed portion of Jupiter is too many EV stops below the exposure of the rest of the shot, so it appears black. Just like in earth photos.

[A.S.I.G.N. Observatory]

Nearly ALL space photographs are enhanced.

Example:

To take a photograph of Jupiter at home through my telescope:

I use a webcam at 10-15 frames per second through the scope to take a 3 minute video.

At the end, I go through the resulting frames one at a time and stack all the blurry ones to the left, and all the sharper ones to the right.

I then take a percentage of the sharper ones, and combine stack them to average out the image.

This gets in all the lovely sharp detail, while discarding anything that was not common in each shot.

Some of these objects moves so much due to actual movement or shooting through atmospherics, that this is the only way you can capture a clear image. To do so in a single snapshot, is almost impossible.

Baz.

P.S. Here's the last one I did at home.
http://i32.tinypic.com/1268xhc.jpg
and how I did it....
http://www.asignobservatory.com/index.php?option=com_content&view=article&id=78&Itemid=117

The difference is, mine was done through a small aperture ground based telescope. That one was done in space.