I have long had the dream of improving the lone closeup Voyager image of Proteus. Being Neptune's second largest moon, I always thought it a pity we don't have a good view of it. There is one multispectral set, taken from two or three million km, and a few slightly more distant clear filtered shots. But this lone frame is from only 144,000 km, with a resolution of 1.3 km/ pixel. Only Triton and Miranda technically have better resolution coverage (I am ignoring the moons of Saturn and Jupiter here). Problem is that it is terribly underexposed. I just wish there were two frames. It is amazing what you can do to reduce noise.

Here is the raw frame:


Here is the best I have been able to do so far. I have created some artificial masks to act as multiple frame to artificially reduce grain:



Anyone have any tips? I'd be curious to see what others could do with this.

Ted

[CODE]

Ted: No tips, alas, but i'm amazed with what you obtain from a nearly all black raw image!

Thanks. The thing that makes it really hard to deal with is that on the 256 level scale, the darkest visible areas of Proteus are 14, the brightest 20 (in other words, 7 levels). Most versions of the image I have seen have enhanced the contrast and then blurred the image to create a smoother grayscale. However, lost in that is the fact that the image is very sharp, and the precise location of features such as crater boundaries is lost when the image is blurred.

in one word : BRAVO, Ted.... Exactly what amateurs may share with amateurs!

Wow, one more example of a huge crater taking up a substantial chunk of real estate... the early solar system must have been a heck of a show with all those chunks flying around. Can you imagine what the Earth looked like before the oceans formed and not too soon after the moon was blasted from it...one huge crater on one side of the planet?!?

I'll have a whack at it a little later Ted. I use Photoshop and I've come up with some snappy little tricks for problems like this over the years.

Similar to the mask you made, create a multilayered image with varying amounts of blurring (as well as lowering the contrast) on each layer. Adjust the layer transparencies on a scale that is inverse to the amount of blurring (i.e; the most blurred will be the least visible, or most transparent.) Start with three layers since it is only a monochrome. Lay the grainy image over the top as the final step and adjust its transparency until you like the final product.

(I would use five layers if it was colored and rotate the blur axis for each one - do not separate the color layers during the blurring process on a grainy color image)

Actually, I used Photoshop too. There are quite a few layers I made. They included a version with 2x2 bins and a high-pass filtered version in addtion to blurring. I also included a layer that was enlarged and then reduced. This created an artificial resampling without a great loss of sharpness that did a lot to cut back on grainyness. And before any of that, I created a simple mask to remove the effects of the reseau marks and the fact that the background levels in the image are uneven. I did this using blank Voyager images. I look forward to seeing your results.

Ted

Here are some other versions of the image.

Planetary Photojournal

http://photojournal.jpl.nasa.gov/catalog/PIA00062

NSSDC

http://nssdc.gsfc.nasa.gov/imgcat/html/obj...g2_1138920.html

Views of the Solar System

http://www.solarviews.com/cap/nep/proteus.htm

Good work, Ted. I got the raw image and barely was able to see anything after twiddling with gamma/brightness/contrast.

Of interest, just below center, there appears to be a broad scrape/groove with a 5km boulder at the end. Possibly a low angle, low velocity impact?

Or a cat in the clouds...

--Bill

There does seem to be a raised area at the end of that groove. Far to big and too flat to be a boulder. I think, though, that the whole feature might be just a strange alignment of craters atop the remnants of previous craters. Sort of like this the way Proteus has a strange resemblace to a decayed tooth in this image, Voyager's lone multispectral set.