APOD: Saturn at Night (2012 Dec 22)

Comments and questions about the APOD on the main view screen.
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APOD: Saturn at Night (2012 Dec 22)

Post by APOD Robot » Sat Dec 22, 2012 5:06 am

Image Saturn at Night

Explanation: Splendors seldom seen are revealed in this glorious picture from Saturn's shadow. Imaged by Cassini on October 17, 2012 during its 174th orbit, the ringed planet's night side is viewed from a perspective 19 degrees below the ring plane at a distance of about 800,000 kilometers with the Sun almost directly behind the planet. A 60 frame mosaic, images made with infrared, red, and violet filters were combined to create an enhanced, false-color view. Strongly backlit, the rings look bright away from the planet but dark in silhouette against the gas giant. Above center, they reflect a faint, eerie light on the cloud tops while Saturn casts its own dark shadow on the rings. A similar Cassini image from 2006 also featured planet Earth as a pale blue dot in the distance. Instead, this scene includes icy moons Enceladus (closer to the rings) and Tethys below the rings on the left.

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Re: APOD: Saturn at Night (2012 Dec 22)

Post by Beyond » Sat Dec 22, 2012 5:09 am

It still looks just as GOOD!
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by revloren » Sat Dec 22, 2012 5:43 am

OK, WOW.

But how are we seeing an image of the rings on the upper half of Saturn's disc when the nearside (top) of the rings themselves is obviously in the umbral shadow? The explanation refers to "a faint, eerie light on the cloud tops", but wouldn't such reflected light be quite difuse rather than a clear image of the rings? If it is from light reflected from other parts of the rings, then why why aren't they visible in the part of the umbra outside the planet's disc?

Oh, and my super top-secret close up reveals several other faint specks, probably other moons.

Did I say WOW?

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Re: APOD: Saturn at Night (2012 Dec 22)

Post by ta152h0 » Sat Dec 22, 2012 6:31 am

When Cassini runs outa gas, is JPL planning on crashing it somewhere with its cameras on ?
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by Aristaeus » Sat Dec 22, 2012 6:56 am

Is that a star to the right of Encelydus? Or another moon?

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Re: APOD: Saturn at Night (2012 Dec 22)

Post by Boomer12k » Sat Dec 22, 2012 7:55 am

revloren wrote:OK, WOW.

But how are we seeing an image of the rings on the upper half of Saturn's disc when the nearside (top) of the rings themselves is obviously in the umbral shadow? The explanation refers to "a faint, eerie light on the cloud tops", but wouldn't such reflected light be quite difuse rather than a clear image of the rings? If it is from light reflected from other parts of the rings, then why why aren't they visible in the part of the umbra outside the planet's disc?

Oh, and my super top-secret close up reveals several other faint specks, probably other moons.

Did I say WOW?
I am thinking it is the FILTERS. They gather different light waves. Like how can we see clouds on the dark side of our planet in weather photos? Infrared imaging, I am thinking. Same thing here. The filters are only giving us certain wavelengths.

And I agree. WOW. Strikingly good, interesting image.

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Re: APOD: Saturn at Night (2012 Dec 22)

Post by bystander » Sat Dec 22, 2012 8:59 am

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alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by owlice » Sat Dec 22, 2012 9:04 am

Oh, now you show up!!
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by Guest » Sat Dec 22, 2012 9:26 am

Boomer12k wrote:
revloren wrote:OK, WOW.

But how are we seeing an image of the rings on the upper half of Saturn's disc when the nearside (top) of the rings themselves is obviously in the umbral shadow? The explanation refers to "a faint, eerie light on the cloud tops", but wouldn't such reflected light be quite difuse rather than a clear image of the rings? If it is from light reflected from other parts of the rings, then why why aren't they visible in the part of the umbra outside the planet's disc?

Oh, and my super top-secret close up reveals several other faint specks, probably other moons.

Did I say WOW?
I am thinking it is the FILTERS. They gather different light waves. Like how can we see clouds on the dark side of our planet in weather photos? Infrared imaging, I am thinking. Same thing here. The filters are only giving us certain wavelengths.

And I agree. WOW. Strikingly good, interesting image.

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I think there is a simple explanation: the greenish color is present over the whole upper part of Saturn, but behind the denser parts of the rings it is not visible.

Anybody: what is the blueish color at the bottom? Is it part of the ring system? If so: why does it appear as if it is not parallel / concentric with the rings?

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Re: APOD: Saturn at Night (2012 Dec 22)

Post by owlice » Sat Dec 22, 2012 10:21 am

[aside] The 2013 APOD calendar is now available for downloading. [/aside]
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by neufer » Sat Dec 22, 2012 12:44 pm

Guest wrote:
Anybody: what is the blueish color at the bottom?
I'm guessing Zodiacal light.
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by Psnarf » Sat Dec 22, 2012 2:40 pm

The infra-red image at http://s3.amazonaws.com/ciclops_ir_2012 ... 7741_1.jpg has a different perspective on the glowing dust. In that image, it appears to be in the same plane as the rings, but more distant from the planet. Gegenshein and zodiacal light would appear if we were looking away from the planet with the sun behind us. Wouldn't there be a mirror image above Saturn if the glow was reflected off of interplanetary dust?

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Re: APOD: Saturn at Night (2012 Dec 22)

Post by neufer » Sat Dec 22, 2012 3:01 pm

Psnarf wrote:
neufer wrote:
Guest wrote:
Anybody: what is the blueish color at the bottom?
I'm guessing Zodiacal light.
The infra-red image at http://s3.amazonaws.com/ciclops_ir_2012 ... 7741_1.jpg has a different perspective on the glowing dust. In that image, it appears to be in the same plane as the rings, but more distant from the planet. Gegenshein and zodiacal light would appear if we were looking away from the planet with the sun behind us. Wouldn't there be a mirror image above Saturn if the glow was reflected off of interplanetary dust?
Backscattering Gegenshein would appear only if we were looking away from the Sun.

Forward scattering Zodiacal light appears brightest close to the sun (in dark skies)
if we were looking towards the Sun with the Sun behind the planet.

The Zodiacal light is symmetric around the Sun not Saturn.

In the APOD the Sun is obviously (based upon the atmospheric sunset brightening)
hidden behind the lower right portion of Saturn.
  • OTOH:
Last edited by neufer on Sat Dec 22, 2012 6:36 pm, edited 1 time in total.
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by LocalColor » Sat Dec 22, 2012 3:57 pm

Wow!

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Re: APOD: Saturn at Night (2012 Dec 22)

Post by Beyond » Sat Dec 22, 2012 7:01 pm

Saturn sure is photogenic :!: :!: Must be all those hula-hoops :!: :mrgreen:
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by orin stepanek » Sat Dec 22, 2012 9:15 pm

A most unusual Saturn photo but I like it! :) :clap: :yes: :thumb_up:
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by ta152h0 » Sun Dec 23, 2012 1:15 am

wow, and I thought this was going to be the last APOD I would ever see, if you believed the Maya bs. But like the song Camp Grenada, the kids wake up the next day and the sun is out, kids are swimming, the canoes are full..........
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by Beyond » Sun Dec 23, 2012 3:40 am

ta152h0 wrote:wow, and I thought this was going to be the last APOD I would ever see, if you believed the Maya bs. But like the song Camp Grenada, the kids wake up the next day and the sun is out, kids are swimming, the canoes are full..........
Your wish is my command... oh beerded one :!: :mrgreen:
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Re: APOD: Saturn at Night (2012 Dec 22)

Post by Spif » Sun Dec 23, 2012 6:51 pm

Guest wrote:I think there is a simple explanation: the greenish color is present over the whole upper part of Saturn, but behind the denser parts of the rings it is not visible.

Anybody: what is the blueish color at the bottom? Is it part of the ring system? If so: why does it appear as if it is not parallel / concentric with the rings?
Keep in mind that the green and blue colors are actually false. The image we see on APoD is really a merge of three monochrome images: one in infrared color, one in red, and one in violet. Whoever did the merge had to assign a weight to the pixels from all three images to produce colored pixels. It looks to me that his choice of color weights was made to tint the rings to approximate the color of the surface clouds of Saturn. The green and blue parts are artifacts that come out from that choice. That just means that those pixels are brighter and brighter still on the violet filtered image than on the other filtered images. The range of shift toward that violet end of the spectrum is not necessarily the same amount of color difference that we would see with our own eyes.

I think it's probable that if we were looking at Saturn directly from a spacecraft, it would all look very monochrome, probably slightly off white... In reality, the variations in hue are probably very slight and maybe only a trained artist would even be able to notice any color differences.

I'm guessing that the rings probably really appear more a dingy white in reality.

-s

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Keep Saturn in Saturnalia

Post by neufer » Mon Dec 24, 2012 6:03 pm

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