Unusually colored northern hemisphere of Saturn seen in this low phase, wide angle view:

Saturn and 4 moons:

Tethys on 2007-10-29:

Just for fun, a collage of four different wide-angle filter combos:



Top left: IR4-GRN-VIO
Top right: IR4-IR3-IR2
Bottom left: GRN-BL1-VIO
Bottom right: RED-GRN-BL1

The moons are overexposed so were artificially turned gray in the shots.

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Saturn, rings, Pandora, Titan, Enceladus, Tethys, and Janus, October 27, 2007.

I used the red, green and blue spectral filter wide-angle images W00037073-5 and W00037126-8 to create this true-color view. I cheated with Janus - it was actually taken with the planet's RGB set, not with the other moons. This image is featured as the cover and as April in my new 2008 Cassini wall calendar, Seasons of Ice and Shadow #3

"A stately Saturn poses for a portrait with five of its moons in this Cassini spacecraft wide angle camera view. From the left, the moons are Pandora (84 kilometers across, a faint speck near the tip of the rings), Titan (5,150 kilometers across), Enceladus (505 kilometers across), Tethys (1,071 kilometers across), and Janus (181 kilometers across). The image was taken on October 27, 2007 at a distance of approximately 1.86 million kilometers from Saturn."

Images from my new 2008 Cassini wall calendar, Seasons of Ice and Shadow #3:
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PIA08387 redux (details):
While on final approach for its Sept. 2007 close encounter with Saturn's moon Iapetus, Cassini spun around to take in a sweeping view of the Saturn System. In addition to the five wide-angle camera footprints that swept across the scene, Cassini also took narrow-angle RGB closeups of each of the moons in the scene. From left: Dione, Enceladus, Mimas, Rhea, Tethys, and Titan.

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PIA07628 redux: It turns out that this lovely grouping of Dione, Tethys and Pandora near the rings was actually part of a series, which included a wider view of the rings and images taken using red, green and blue spectral filters. I combined the true-color version with clear-filter views to create this true-color version of the monochrome image released as PIA07628.


Full: http://www.flickr.com/photos/ehartwell/2037497533/

PIA08366 redux: It turns out that the lovely view of Rhea against Saturn's quadrant is actually part of a full hemisphere version that includes Prometheus as a faint speck just below the rings at bottom left. I combined both sets of RGB images and tweaked the colors to match the Photojournal version.

Lovely shot of Saturn and Rhea. Not only do you have a ring moon visible (I don't think it's Prometheus, though - way too far from the rings and on the wrong side of F ring. Janus? Epimetheus?), you also seem to have its shadow at top, immediately to the right of a camera artifact.

I actually did that Dione - Tethys - Pandora mutual a while ago as well, from calibrated PDS raws. Mine doesn't have the horizontal expanse of your image, but it's interesting to compare colors in both shots.

Good point about the ring moon - it really *is* too far out to be Prometheus. We have to guess until the PDS release gives the actual time for the left half of the image (W00024032), but the Solar System Simulator and Celestia both put the right half (W00024022) at around 2007 02 04 04 04:20. Unfortunately, SSS doesn't show the small moons, but running Celestia suggests the moon at that position would be Prometheus just past 04:20, Mimas around 08:12, or Epimetheus around 09:02.

I hadn't even noticed the shadow near the top. And is that another moon to its left? Celestia puts Mimas around that location at 09:02, the same time that Epimetheus was at the lower moon's position. According to Cassini Significant Events for Sunday, February 4 (DOY 035): "Saturn with all of its rings and its satellites Dione and Telesto were captured together in a single image. Tethys, Mimas, and Epimetheus starred in another image with the rings." Hmmm... Time for another close look at the raw images.


Yours has the more realistic color. I should have mentioned this one was tweaked for the calendar. CafePress does a superb print job, but paper just can't provide the dynamic range you need for decent ring detail. I find I need to lighten the shadows so they don't fade into black. Then, as happened here, I often boost the saturation a bit to compensate.

Celestia's ephemeris for small moons is not accurate enough to give any remotely precise location to the moons. Luckily, this is where Saturn Viewer comes in. Plugging in your estimated time, it would appear the moon in question is Janus. Prometheus and perhaps Pan also ought to be detectable in the raws a bit ahead of Janus. I think it's Janus's shadow up there as well. The little dot to the left of the shadow is a camera artifact, you can see it in the right half as well.



I can't wait till this period (Jan 2007 - Mar 2007) hits PDS, there'll finally be some low phase Saturn stuff in there after quite a while spent basically on the night side.

Thanks for the save, Gordan! I'm going to identify it as Januas and its shadow (good thing CafePress is print-on-demand). And bless you for pointing me to the Saturn Viewer.

Here are some HST images I recently worked on. I have also posted some of my work on HST Galilean imagery in this thread.

This view is from March 7, 2003 using a mosaic of ACS HRC Images. The rings were clipped except for one image on the left side, which I used to extend both sides beyond the edges of the original image, along with WFPC/2 images taken within about an hour of the set.

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Also, I have reprocessed the old August 26, 1990 view. It is relatively limited (there were only three filters used, and it was taken using the wide field chips, not the planetary camera). Still, it is (at least to my knowledge, Hubble's first look at a planet.

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Fantastic! - how Galileo would have loved these!!!!!

I started to ask you what in the world you were talking about....then I realized you were talking about Galileo Galilei, not the Jupiter orbiter!

Here is a more primitive processing of the data (without the ring reconstruction and enhancements to bring out more detail).

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Also, today's Cassini release is neat...It has a real Pioneer-ish feel.

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Interestingly one can see Saturn's blue winter hemisphere through the Cassini Division and this is a pre-Cassini image. I have always found it strange that as far as I know the blue color was an unknown phenomenon before Cassini imaged it. This is remarkable - I have even managed to image it using a 6" telescope and a webcam after the northern hemisphere became visible from Earth due to the decreasing ring opening angle. I also think that observing visually I have seen hints of the color but it should be noted that I wouldn't have noticed it without knowing it was there .

I am guessing here (I haven't worked on the issue myself), but maybe this effect is lost with Voyager's OGV, GVUV, and whatever else color shifts.

It should have been more than readily apparent in the violet filter. The reason it was absent was probably the proximity of equinox. Saturn's northern color is fading again as ring shadows move towards the south.

Yes, but with color shifting, it would have looked green or yellow.

Bjorn - yes that is funny about how such an interesting discovery can be hiding in plain sight. I think I could also see this in my friend's earthbound CCD imagery from a few years back. I'll have to try this visually in a telescope, though another good opportunity might have to wait a long time?

So is Saturn a part-time local Neptune?

Not-so-plain sight. As Ugordan pointed out, it is fading as equinox approaches. Pioneer 11 was just before equinox, and Voyagers 1 and 2 were not too long after. From Earth, the rings obscure the winter hemisphere. Since the rings are brighter than the disk, it makes the bits of the blue area one can see through and behind the rings visible in low resolution images hard to notice.

It should be noted the rings only appear brighter than the planet at low phase angles (as seen from Earth). They grow dimmer with increasing phase angle and their "dirty" nature becomes more apparent as brownish coloration.

In any case, it shouldn't be that surprising Saturn would acquire a bluish hue when the sunlight is significantly reduced - both Uranus and Neptune share a similar color. It remains questionable, however, just how much Saturn cloud activity is driven by internal heat.

That is true. Still, during either hemisphere's deep winter, they are always illuminated at a low phase angle.

They are looking for new moons again. I took an a plastic sheet and a marking pen and found 5 moving objects against the stars in the first 3 pages of images. My prblem is that I don't really know to figure out what I am finding using any of the programs out there. I'm sure sure some of you here might be able to "co-discover" something new in this recent batch of images. Also would make great movies
-Floyd

I'm not usually a rings person especially but this is an exceptional image, I think:

http://ciclops.org/view.php?id=3885

This is quite a decent WAC view of Saturn that I've quickly put together:

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and here's a version that's registered on the atmospheric features, as opposed to the rings and limb:

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Nice one. Why don't you merge the two? I leave the green channel static and let the red and blue channel "move around" to best register the certain features such as moons, clouds and then overlay all the different registrations onto a single image and applying transparency to get the best of all worlds.
Why green channel? Most of the energy seen by the eye is there and with leaving that one unchanged you minimize visible distortions introduced by selective merge of different regions.

Here's my take on the wide angle shot. I believe the moon transiting Saturn's disc is Mimas.

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I had a go too... got some colour fringes, n hemisphere is a bit too blue, and three Mimases against the disc there, but on the whole pretty pleased with it

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Gordan,

I'm always keen to improve my image processing skills, so I'm very grateful for your advice indeed. However, I'm having a little trouble understanding what you mean by "applying transparency to get the best of all worlds".

Do you mean that I should have two sets of Red and Blue raws in a single image, aligning one set with the limb and rings, and the other with the clouds? Then selectively combining different areas of the two Red and Blue layers so that they align with the static Green layer?

That's what I've done to achieve the following result (although I haven't bothered to properly align the separate Mimas apparitions):

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Thanks for your help,

Ian.

I mean you make two (or more if required) copies of RGB sets, each aligned on something (but you align the R and B channels, leaving G fixed) and then you stuff them all into one image as layers and apply transparency masks so each of the best registered layers shows only that part, while other layers show the rest. For example if your first layer is aligned on the disc, but not on cloud features, you make a second one that registers clouds best and overlay it over the base image. Create a transparency mask so that the second image is transparent at the limb (and whereever you have color fringing) so that it shows the base image.
That gives a visually appealing result for Saturn. Not so much for Jupiter as its cloud features are very much more obvious and don't fade into the haze near the limb.

Thanks for the further explanation Gordan - everything seems clear in my mind now!

...and nice image Stu: I like the 'enhanced' colours!

Here's my attempt to put together the 3-frame WAC mosaic, taken through the Clear and IR3 filters:

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Ahh, you beat me to it, Ian.

Here's my attempt at color, with some cheating at Saturn's overexposed limb (applied a clear filter frame at that portion) at left:



And here's a different contrast (decreased gamma) version as sort of a complement to this view, pretty similar phase angles:



EDIT: Improved the overexposed limb appearance somewhat in the second image version. It doesn't jump out as much now.

Edit: That's excellent Gordan! Why don't you submit it to APOD?

A couple of nice limb shots, featuring Mimas and Prometheus:

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A desktop-size merge of the above two images:

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Meanwhile, vote for Your favorite image at:
http://ciclops.org/contest07.php

There's a lot going on in this mosaic:

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At a guess I'd say that's Dione casting a shadow onto Saturn's northern hemisphere, but would need to check. Nice bright storm in the southern hemisphere too.

It is a busy set of images. I am not sure Dione can cast shadows yet. My vote is for Tethys.

I think it might be Tethys as well, it's brighter than other stuff visible (though that's a risky statement with raw jpeg footprints). That's probably Dione to the right, with a hint of dark terrain. Nice catch on the big storm previously detected by its radio emissions. The Dragon Storm 2?

My attempt at some color:


EDIT: Yep, those are Tethys and Dione with Enceladus at the far side. Additionally, Epimetheus and Pandora are detectable as small specks about halfway between Enceladus and Dione. Prometheus was around as well, but it's lost in front of Saturn's disc.

Fantastic picture, gordan!

Thanks, Marco. I'm particularly interested in low phase views such as this one as they seem to bring out much more variation in Saturn's atmospheric bands than what your typical medium-phase Cassini view shows. I don't know how much the color here can actually be trusted, but its striking that the northern hemisphere displays such discrete colors.
I guess sunlight coming straight down (well, as straght down as is possible at those latitudes at the moment) and reflecting straight up to the observer really helps reduce atmospheric scattering and absorption of certain wavelengths. It's at these phase angles that Saturn starts to look the way we see it from Earth. That's why it's a particular shame another big low phase mosaic (from below the ring plane) from February 2007 was overexposed.

Here's a 'work-in-progress' version of the latest mosaic:

Edit: I've adjusted the colours to something approaching the right balance; now all I need to do is register the moons and clouds...

Edit: Clouds are registered, now for the moons...

The finished product:

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Incredible!

...closest thing any of us now living will ever come to seeing the real thing from this vista.

Thank you for the gift, Gordan.

Just for fun I made a flicker GIF between the two recent mosaics, click here to get it (1.4 megabytes). I may add in additional mosaics later, should any appear.

Another quick one:

Nice view and interesting that more of the small-scale circulation features are visible in the bluer regions, probably in relation to having less (yellowish) high-altitude haze/clouds.