Exquisite Saturn Images Options

[mars loon]

Here's a short GIF animation showing Cassini approaching the ring plane from below. Note how several atmospheric features can be seen moving from West to East during the sequence:
[

Ian,

everything in your latest posts is exquisite. Well thank you for the OK and I'd may like to use a few more like the gif too. Gee I have to revise the entire Saturn portion of my talk set for Feb 14 in Philadelphia! forum members welcome
http://www.rittenhouseastronomicalsociety.org/meetings.htm

Suggestion: can you slow down the gif somewhat please? I think it will help the audience appreciate and understand more easily. thanks

ken

[Exploitcorporati...]

Jaw-dropping, amazing work, everyone! I've been waiting for these perspectives for years. One question for ugordan specifically regarding the natural color views: Looking at the difference between your processed images of Saturn and JPL's, the pronounced blue tones in the northern hemisphere seem much more muted in yours. I know next to nothing of the characteristics of the filters or the technical aspects of combining them, but what would we actually see If we were there? I've had many questions from friends about that unearthly (and once-unsaturnly) blue, as it gives the place an unfamiliar look to them. I'm inclined to guess your processing is more accurate, especially as you've cranked out hordes of wonderful color products that JPL seems averse to releasing. Anyways, congrats to Ian, yourself, and others in this thread. I will certainly have a difficult time kicking you off of my desktop.

[Ian R]

Had to improvise a little bit with this one, as there seems to be a Red frame missing, somewhere:

[ugordan]

Exploitcorporations, I can't really say my processing is all that more accurate than JPLs as there are a few things to consider here: The colors in my latest Saturn images in the gallery are based on my experiments with VIMS data and choosing channel mixes to resemble that as closely as possible. I've still to figure out the best mix, but I'm working toward it. If anything, the blue cranium might be a bit too subtle in some of my views. The other thing that might affect your perception is I have a lot of high phase Saturn composites there and I think the blue tones aren't in reality as pronounced in those views. I also tried to keep the saturation lower to match the softness of the VIMS views, especially when a proper 2.2 gamma is applied.

That said, I do believe CICLOPS went overboard with saturation on a few color composites, making other Saturn shots weirdly yellow and dull compared to those. For reference, here are two of my ISS views that closely resemble results using VIMS: Ring Shadows 1 and Saturn's North. Compare the second one with the Blue Cranium official release.

Just for a quick reference, here are some of VIMS results with a slightly lower gamma and compare the intensity of the colors there. Also, a VIMS mosaic of the blue cranium from a low phase angle.

[volcanopele]

If it is any consolation, ugordan, that's what I always get for my Saturns, a more grayish northern hemisphere than bluish.

[ugordan]

A simple RGB composite will tend to give you that, but you'd need to mix the channels in a right ratio to compensate for the effect of different bandpasses and the fact green channel overlaps quite a bit with the other two. It comes down to sensibly "fudging" to match what the scene actually looks like. Worse, different targets often require different mixes -- Jupiter would turn out quite weird with the same mix as used on Saturn, even with the same filter sets. The "correct" mixes might even vary with phase angle, but I might be wrong on that one.
Really, you loose a bit of "true" color information by using only three color snapshots (opposed to full visible spectra) and that's why I give more weight to VIMS produced colors as they are more "scientific", taking into consideration human eye specifics. Especially since they pass reality checks such as white Enceladus and gray Mimas. Neglecting weird bluish Venus colors and a brownish Moon here.

But, yeah, I think some of you at CICLOPS might have gotten a bit carried away with a few composites.

[Exploitcorporati...]

Thanks ugordan for the insights. I missed your referenced VIMS post...very interesting stuff. I need to study up on gamma correction. As an aside, no offense intended toward CICLOPS, especially regarding the icy satellite mosaics. The only important colors there are the sickly green of envy (VP-that's your mosaic of Enceladus from the Feb. 2005 NT encounter? Mine still looked like a Hockney collage after two years of struggle!) and the cool auzere of the blue screen of death.

[dilo]

Waiting for another Ian stunning stitch, I played with the last pictures taken on Feb,6:

First one is an RGB combination, the latter is a pseudo-color image based on MT3, green and B3 filters.

[Ian R]

Oooh, very pretty indeed dilo!

Here's my composite, with colour adjustment based on Gordan's earlier advice:

[Ian R]

...

BTW, that latest image is great! It's so Voyager-esque. In fact, you can use that moon that's visible to correct the colors a bit, make it turn white and you'll have colors closer to calibrated ones. Usually you can't rely on stuff like that, though. Did you use the violet or blue filter, this looks to me like it's violet?

Cassini spent so much time on the night side that I lost track of just how south ring shadows have actually moved.

I took the liberty of tweaking your image a bit, I hope you don't mind

Gordan,

Interesting indeed to read your account of assembling Cassini colour composites. With the mosaics that consist of two footprints only, my approach has always been to carefully align and join the Green raw images first, and then to use that as a geometric template for aligning the Red and Blue channels.

All of these images use RGB - I haven't actually tried the Violet filter yet, and probably wouldn't anyway, unless the Blue image was missing or corrupt. In any case, the colour adjustments you and Dilo have applied to the mosaics look great!

Cheers.

[Ian R]

Suggestion: can you slow down the gif somewhat please? I think it will help the audience appreciate and understand more easily. thanks
ken

Hi Ken,

Yes, please feel to use any of my images and animations in your talk - I'm only too glad to see them reach a wider audience!

Here is a rotated and slower version of the first animation:



Is this right speed, do you think? Are there any other adjustments you would like to see?

Ian.

[Ian R]

Here's a quick rotation movie, using the CB2 and IRP0 filters:

[um3k]

Here's my composite, with colour adjustment based on Gordan's earlier advice:

Hey Ian, would it be alright with you if I place that image in the astronomy club newsletter I edit? It's a beautiful picture, and I'm running low on content this month. I do need to know how you want to be credited.

Thanks,
Justin

[ElkGroveDan]

-

Wow again Ian!

[Ian R]

Hey Ian, would it be alright with you if I place that image in the astronomy club newsletter I edit? It's a beautiful picture, and I'm running low on content this month. I do need to know how you want to be credited.

Thanks,
Justin

You're more than welcome to use the image Justin. I think the best credit would be the one that Emily used on the Planetary Society blog:

NASA / JPL / SSI / Ian Regan

Good luck with the newsletter.

Cheers,

Ian.