29-30 August 2007 Icy Satellites (rev 49), Last stop on the road to Iapetus |
29-30 August 2007 Icy Satellites (rev 49), Last stop on the road to Iapetus |
Sep 2 2007, 12:52 AM
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#46
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Yes, there are some "chain" features on Tethys as well, but it's not as striking as on Rhea, and it always seemed to me that the ones on Tethys were near and generally radial to the big basin.
I also noticed some chain-like features in the only close-up images we have of Iapetus, but again, they're not as ubiquitous as the ones on Rhea. I haven't noticed the same thing at all on Dione or the older portions of Enceladus. -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Sep 2 2007, 01:59 PM
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#47
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Member Group: Members Posts: 270 Joined: 29-December 04 From: NLA0: Member No.: 133 |
A quick 11 frame crescent Rhea:
http://paranoid.dechengst.nl/saturn/Rhea-1...29-AUG-2007.jpg (1.5 MB) -------------------- PDP, VAX and Alpha fanatic ; HP-Compaq is the Satan! ; Let us pray daily while facing Maynard! ; Life starts at 150 km/h ;
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Sep 2 2007, 03:14 PM
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#48
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
Wow! Nice work.
I can't imagine what that terrain must look like from the surface - a global badlands of immense vertical scale. -------------------- If Occam had heard my theory, things would be very different now.
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Sep 2 2007, 05:39 PM
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#49
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Junior Member Group: Members Posts: 61 Joined: 17-September 05 From: Sweden Member No.: 499 |
Wow indeed! I always loved the crescent images and that mosaic is just incredible.
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Sep 4 2007, 08:01 AM
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#50
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Member Group: Members Posts: 599 Joined: 26-August 05 Member No.: 476 |
Badlands is apt. Place looks like a setting for some sky-fi about space smugglers or such.
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Sep 4 2007, 05:26 PM
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#51
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
It works pretty well to copy the area, paste it as a new layer, then nudge it one pixel up or down and select a filter that shows the max of the two layers' brightnesses. Basically, close the even numbered lines onto the odd ones. Which Photoshop filter does this? I've looked around and I can't find an obvious one. My trick for this has been to take a mask that I've made with alternating black and white lines, paste it onto the image, erase away the part of the mask that I don't need (covering the part of the image that is not affected by the truncated lines, then use the wand set to no antialiasing and non-contiguous pixels to select the lines from the mask that cover up the black pixels in the underlying image, then go to the underlying image, shift the selection by one pixel up or down to get to the good pixels, copy and paste. Using a filter that takes the maximum pixel value would be much much easier than this!! --Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Sep 4 2007, 05:32 PM
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#52
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
What you need is to deinterlace.
For this image: http://saturn.jpl.nasa.gov/multimedia/imag...3/N00090982.jpg Filter > Video > De-Interlace > Even Fields and Interpolation. Not perfect, but it does the job. Doug |
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Sep 4 2007, 05:36 PM
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#53
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
Ideally, if the missing lines were all totally black, you could expand the canvas size to the right by say 1 pixel using black color and magic-wand the entire right side and select all the missing lines in one go. Since jpeg messes this up, you can increase the tolerance somewhat to compensate.
I don't know if it's me, but sometimes the deinterlace filter needs to be set to odd lines instead, could depend on the selection or something. -------------------- |
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Sep 4 2007, 05:38 PM
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#54
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
Which Photoshop filter does this? I've looked around and I can't find an obvious one. My trick for this has been to take a mask that I've made with alternating black and white lines, paste it onto the image, erase away the part of the mask that I don't need (covering the part of the image that is not affected by the truncated lines, then use the wand set to no antialiasing and non-contiguous pixels to select the lines from the mask that cover up the black pixels in the underlying image, then go to the underlying image, shift the selection by one pixel up or down to get to the good pixels, copy and paste. Using a filter that takes the maximum pixel value would be much much easier than this!! --Emily It's not a filter per se -- I just create a second layer and paste it on top of the original layer. Then under the layers menu, you have many options for which logical rules apply pixelwise to the layers, and one of them is Maximum/Brightest. That's a whole wonderful side of Photoshop, playing with layers, logical rules, and transparency. The other thing it's useful for is colorizing high-res BW images with a low-res color layer. I'm away from the computer on which I have Photoshop installed, so if this description seems unhelpful, let me know and I'll repost while running Photoshop. |
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Sep 4 2007, 06:22 PM
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#55
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
OK, I've now done a side-by-side comparison of three methods of removing the every-other-line truncation: de-interlacing, taking the maximum of two layers, and my laborious method described above. De-interlacing seems to do the best job of the three because of the interpolation step. And you can even get away with applying it to the whole image (which effectively throws out half of the image's original pixels, replacing them with pixels interpolated between the remaining pixels) without very much loss of detail, even for these Rhea-crescent pictures, which are full of detail. It's better to select the area with the truncated lines and just apply the filter to that, but if you want to do a quick-and-dirty job the quality doesn't suffer much if you batch process a whole folder's worth of pictures.
The three strips below were produced from N00090982.jpg, with the Maximum, De-Interlace, and my methods applied to the corner that had the truncated lines. --Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Sep 4 2007, 07:46 PM
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#56
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Senior Member Group: Members Posts: 1669 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
Hi all,
I've been working in IDL so I wrote a procedure to find how much of the line is black (or near black beyond a threshold), then take the average of the two surrounding lines. This is similar to one of Emily's methods I think. I'll post it at this URL if you'd like to sort through the logic... http://laps.noaa.gov/albers/idl/clean_ortho.txt A good input threshold to use I find is around 27. -------------------- Steve [ my home page and planetary maps page ]
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Sep 4 2007, 08:12 PM
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#57
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Very sneaky, Steve! Wish I had IDL. I know it's possible to export freestanding IDL applets (.sav files) that can be run with IDL Virtual Machine...don't suppose you'd want to give that a try...
--Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Sep 4 2007, 09:44 PM
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#58
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Senior Member Group: Members Posts: 1669 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
Interesting as I'm a novice with the IDL virtual machine. I tried making a .sav file if anyone would like to test it, assuming it can be downloaded for that purpose from my site:
http://laps.noaa.gov/albers/idl/clean_ortho.sav -------------------- Steve [ my home page and planetary maps page ]
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Sep 4 2007, 10:07 PM
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#59
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Thanks for the attempt! It didn't work; I got an error:
QUOTE The following error was encountered; Attempt to call undefined procedure/function: 'CLEAN_ORTHO'. Please consult the supplier of the application. Oh well! It was worth a try, but I suppose there's no need to get fancy; De-Interlace works just fine for my purposes.--Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Sep 5 2007, 12:49 AM
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#60
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
Great explanation of how a mosaic is made and how Cassini images are compressed on your blog. One little suggestion. I select only the area that contains truncated lines to deinterlace. That way, the resolution isn't needlessly impacted for the rest of the image.
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