Celestia Forums

t00fri wrote:Here is a false color-enhanced image from this morning Tue 26th 8am UTC:

Bye Fridger

How are you "enhancing" these images, Fridger? Are you combining images taken with different filters? Or just tinting a single image and stretching the histogram?

Evil Dr Ganymede wrote:

t00fri wrote:Here is a false color-enhanced image from this morning Tue 26th 8am UTC:

Bye Fridger

How are you "enhancing" these images, Fridger? Are
you combining images taken with different filters? Or
just tinting a single image and stretching the histogram?

Evil Dr. Ganymede,

I use the standard technique of mapping the gray shades
of an image onto a suitable gradient of colors. Each
image manipulation program offers a great variety of
such gradients. One can also make new ones, of course.


This effects that the subtle differences of the gray shades
become more clearly visible due to the added color
degrees of freedom.

In addition, I tend to carefully add a small amount of
"unsharp masking", again a standard technique of image
enhancement. 'Enhancing contrasts' or 'sharpening'
represent much more radical changes to the original
image, which I always try to avoid.


Stacking many images on top of each other is certainly a
very effective technique, notably also to reduce inherent
noise. This works only, however, if precise alignment
markings are available on the various images.

Bye Fridger

I have given Cassini a makeover-hopefully it looks a little more realistic

If you have Celestia v1.3.2 installed you should download this one here
http://celestiamotherlode.net/creators/jestr/Cassini%20v1.3.2.zip
If you have other versions go here
http://celestiamotherlode.net/creators/jestr/Cassini%20v1.3.1.zip
It doesnt look as good in the older versions though (depth sorting I guess)
All the best Jestr

An image-processing trick I sometimes do is to either subtract or divide one of the featureless-looking images from one of the images taken with the surface-detail-revealing filter (if you subtract, you first need to dim the subtraction image to prevent the subtraction from blanking everything out completely). That removes most of the effect of varying illumination angle, so that then I can jack up the contrast to bring out faint surface albedo features without losing less brightly lit areas.

I have a nice picture made from two of the frames in Cassini's last image download that I made this way yesterday, but the site that I use to host images seems to be completely shot today, so there's little point in linking it.

http://www.cidehom.com/apod.php?_date=041026



!!

symaski62 wrote:http://www.cidehom.com/apod.php?_date=041026

!!

That's an image from the last flyby, not this one.

I have no idea what to make of this, but I don't think it looks like Ganymede

That last picture was actually from the first flyby a few months ago.

Here's one from a few days ago-- someone at JPL did the same trick I just described,
only with higher-resolution versions, and then they unsharp-masked it afterward:

http://photojournal.jpl.nasa.gov/catalog/PIA06125

Do check out the full-resolution version. The dark area has what look like impact craters in it.

I could be completely off base here, but to me that looks like nothing so much as a frozen lake surrounded by higher, ridged terrain.

VIMS said back in the summer that those dark areas were mostly water ice, right? It looks like it pooled there.

Matt McIrvin wrote:That last picture was actually from the first flyby a few months ago.

Referring here to szymaski's last post. I see Chris beat me to the Photojournal link.

Oh, and lookie here-- hot off the high-gain antenna:

http://saturn.jpl.nasa.gov/cgi-bin/gs2.cgi?path=../multimedia/images/titan/images/pia-titan-1-2.jpg&type=image

The same area, closer up...

This one's even better - take a look at the image on the right. LOTS of detail there.
http://photojournal.jpl.nasa.gov/catalog/PIA06125

Buggered if I know what's going on there! Radar data should be coming back in about 15 minutes from now, as I write. Dunno when that's going to be publicly available though...

I applied the same massive-unsharp-mask treatment to that closer-up image that JPL just released. It looks like some of those light spots in the dark area have wispy tails, as if material is/was blown off of them. And there's something that looks like a crater with a teardrop-shaped extension, kind of like those craters in old Martian stream beds.

And those weird darker streaks all over the light regions... I'm not even going to guess what's going on there.

But my first reaction to these pictures was "Snowball Earth."

Evil Dr Ganymede wrote:

symaski62 wrote:http://www.cidehom.com/apod.php?_date=041026

!!

That's an image from the last flyby, not this one.

http://antwrp.gsfc.nasa.gov

Matt McIrvin wrote:But my first reaction to these pictures was "Snowball Earth."

My first reaction is "I really don't know what the hell I'm looking at"
The images are still too unclear at this stage to recognise features. Heck, we can't even see anything resembling obvious impact craters.

We need that radar data to make sense of this, I fear.

Seems that Titan's hellbent on holding onto its secrets til the bitter end .

Matt McIrvin wrote:Oh, and lookie here-- hot off the high-gain antenna:

http://saturn.jpl.nasa.gov/cgi-bin/gs2.cgi?path=../multimedia/images/titan/images/pia-titan-1-2.jpg&type=image

The same area, closer up...

and here is my false-color/ unsharp mask enhanced version:



Bye Fridger

I wonder about that big dark feature. (Xanadu?) It looks like an ocean with some islands in it, but it is supposed to be a continent, isn't it? The edge looks very much like a coastline from a distance, but close up, the border isn't that sharp. Could the blurriness result from a sludgy substance, say a sort of glacier or something?

Anyways, are the pictures seen radar images or regular ones?

ArneB wrote:I wonder about that big dark feature. (Xanadu?) It looks like an ocean with some islands in it, but it is supposed to be a continent, isn't it? The edge looks very much like a coastline from a distance, but close up, the border isn't that sharp. Could the blurriness result from a sludgy substance, say a sort of glacier or something?

Anyways, are the pictures seen radar images or regular ones?

These pictures that show detail are in the infrared, taken with a specific filter designed to look through the haze.

Xanadu is the name given to the bright feature to the east of the dark one. That particular dark feature doesn't seem to have a widely-agreed-upon name, though I've seen analyses of Hubble and Voyager photos that referred to it as "the Sickle", so that's what I've been calling it.

The blur at the edge might just be from atmospheric haze blurring the picture. But, as I said, when I try to unsharp-mask that out, some of the bright spots still seem to have wispy tails extending from them.

Dr. Ganymede's right; we need that radar data. There's already some VIMS data released; JPL put up a little movie of the whole disk of Titan seen in frequencies sliding through the electromagnetic spectrum.

I have to admit I'm not terribly impressed with these pictures. Maybe there is more to come. At 745 miles at the claimed resolution I expected more at least in the way of atmospheric features.

I'm getting the impression that Titan is much like Venus in that the visible surface will be forever shrouded by the haze. The radar data will be way more telling than visible light.

What is that strange circular artifact in all the pictures I've seen so far? Always in the same place of the frame.

Hoover wrote:I have to admit I'm not terribly impressed with these pictures. Maybe there is more to come. At 745 miles at the claimed resolution I expected more at least in the way of atmospheric features.

There's a load of really closeup images on CICLOPS:
http://ciclops.lpl.arizona.edu/view_event.php?id=6

And they reveal absolutely nothing. I too am somewhat surprised at just how indistinct and blurry the images are, even close up.

I'm getting the impression that Titan is much like Venus in that the visible surface will be forever shrouded by the haze. The radar data will be way more telling than visible light.

Apparently it's being processed now...

What is that strange circular artifact in all the pictures I've seen so far? Always in the same place of the frame.

Believe it or not, it's a dust spot on the lens . Voyager had a few of these too.

I'm reminded of Triton by these pictures. No cantaloupe terrain, but there are those dark spots/streaks on the lighter areas. Aren't Triton and Titan pretty much identical, other than the obvious size and atmospheric differences?