Io Blog |
Io Blog |
Feb 26 2008, 08:50 AM
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Senior Member Group: Moderator Posts: 3241 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Just let you all know about a new blog I've started called The Gish Bar Times located at http://gishbar.blogspot.com/ . I intend to use the blog to cover Io-related news like new papers or abstracts, developments with the flagship mission selection process, newly processed images, volcano news, or pretty photos taken of Io and Jupiter. I hope you all enjoy!
-------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Aug 19 2010, 11:18 AM
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Senior Member Group: Moderator Posts: 3241 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Bjorn has touched on this earlier and has his own webpage on it, but I thought I would try my hand at creating a true color image of Io using Galileo imagery. I go into much more detail on my blog, but basically I used the ground-based spectra of Io to determine correction factors for combining Galileo violet and green filter images to synthesize an appropriate blue filter. Bjorn used the Voyager blue filter as a guide, whereas I tried to create something that was a little closer to the violet image but using the BL1 filter on Cassini as a guide. No images of Io in that filter are available, I just used the effective wavelength as something I felt was a best-case blue filter.
I post the image here, but I have the nice, pretty charts and graphs (yes, I have finally re-learned how to properly use Excel's chart mechanic, stupid Microsoft and their ribbon instead of a menu...) http://www.gishbartimes.org/2010/08/exposi...rue-colors.html -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Aug 19 2010, 05:40 PM
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
Nice experiment. You bring up a good point about the name of the Voyager "blue" filter, I would just point out that it's actually the "green" filter that's more orange than green, making many of the old Jupiter shots look greenish among other things.
Do you have that visible spectra in tabular form? I'd love to run that through my code to see what color it produces. I threw all your Io Galileo composites through my CIE XYZ linear interpolation code to see how it'd turn out a while back. Here's that same shot (assuming the filters sampled the discrete 665, 559 and 413 nm wavelengths): Having the actual surface spectra might make for a more accurate interpolation, especially that knee at ~520 nm. Looks like the visible spectrum could be well approximated with two or three linear segments. While playing around with Phoenix surface images, I found out that simple channel mixing to get average wavelength works pretty good for most cases, but just doesn't cut it for objects with strong spectral slopes (and hence strong colors) - surface, calibration chips etc. It was only once I gave up on that and interpolated the spectra through 3 (or more) filters and integrated that through the tristimulus values did I get results really close to Mark Lemmon's surface shots. One thing is that a strong red hue translates into a darkening of the blue channel in sRGB gamut which is something just not accounted for with channel mixing. -------------------- |
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