Rev 123 - Dec 18, 2009-Jan 3, 2010 - Prometheus Options

[Stu]

I was struck by how much images like this...

http://saturn.jpl.nasa.gov/multimedia/imag...5/N00148493.jpg

... remind me of the view through my 4.5" scope when I peer into it without the eyepiece. LOts of fascinating internal light reflections there...

[elakdawalla]

I cheat to get color. RGB color combos from Cassini images almost always have some completely white pixels due to the automatic stretching. To set the color I just go grab something Gordan made from calibrated imagery and set the RGB values of that brightest pixel to those of a bright pixel in a Gordan image. It's not science but then images made from raws aren't science either.

Also for the version I posted in the blog I made an RGB combo from red, green, and blue filter images, and also stacked the red, IR, clear, and green channel images to make one that was less affected by JPEG artifacts and noise, then did a nonlinear stretch on it to bring out some more of the detail in the brighter regions, then sharpened it just a little bit. Then I converted the RGB to HSB and swapped in the sharpened image for the clear channel.

[ugordan]

Which is kind of similar to what I did above - selected a small rectangle (for better s/n) in the thick of F ring, removed "dust and scratches" and averaged it and thus got the white point and channel balance, seeing how much each channel needs to be boosted to make that averaged portion gray. In 16 bit mode, of course, every little bit helps. Then just applying those factors to the entire composite. Obviously only works if you have something you know is pretty much white/gray in the source image AND is not overexposed in any channel - F ring, Mimas, Enceladus and leading hemispheres of Tethys and Dione work well here.

When it comes to raw jpegs, we all cheat. Only our methods may differ

[S_Walker]

Which is kind of similar to what I did above - selected a small rectangle (for better s/n) in the thick of F ring, removed "dust and scratches" and averaged it and thus got the white point and channel balance, seeing how much each channel needs to be boosted to make that averaged portion gray. In 16 bit mode, of course, every little bit helps. Then just applying those factors to the entire composite. Obviously only works if you have something you know is pretty much white/gray in the source image AND is not overexposed in any channel - F ring, Mimas, Enceladus and leading hemispheres of Tethys and Dione work well here.

When it comes to raw jpegs, we all cheat. Only our methods may differ

Though we tend to come to similar conclusions. If you decide to try MaxIm, feel free to ask me any questions you'd like via my Sky & Telescope email address.

Happy new year!