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Apr. 2nd, 2005
Haze of Titan
Apr. 2nd, 2005 10:04 amThe atmosphere of crescent Titan, backlit in color:
There's been some discussion in the Celestia forums over whether the blue and violet haze layers of Titan would actually be visible to the unaided eye. But this is a visible-light image and I don't think it's far from natural color (I used a violet-filter shot as well as RGB to bring out some of the higher layers, but tried not to boost the blue too much over what the RGB composite had). I suspect that you'd see those blue layers at least when looking the horns of a crescent Titan.
There's been some discussion in the Celestia forums over whether the blue and violet haze layers of Titan would actually be visible to the unaided eye. But this is a visible-light image and I don't think it's far from natural color (I used a violet-filter shot as well as RGB to bring out some of the higher layers, but tried not to boost the blue too much over what the RGB composite had). I suspect that you'd see those blue layers at least when looking the horns of a crescent Titan.
Another side of Titan
Apr. 2nd, 2005 10:21 am
Finally, we get clearer pictures of something other than Xanadu and the Sickle... The right half of this image was actually photographed in some detail during the distant flyby just after Saturn orbit insertion last summer. The rest has only been seen from much greater distances. This is my rough composite of a couple of wide-angle infrared images, munged to bring out the brightness variations; JPL should have something better before long.
Getting the colors right
Apr. 2nd, 2005 11:43 amIn this picture taken at a less extreme sun angle, the colors of Titan appear more muted:
To an outsider working from the JPL raw image archive, there are a number of uncertainties involved in putting these color pictures together. One is the question of whether the red, green and blue frames all had the same exposure settings. My experience with Cassini ISS camera images is that they're more likely to take roughly comparable exposures for the different color channels than, say, the Mars rover team is, so you can get pretty good color from a simple superimposition, but this is not always the case.
The other uncertainty is whether the frames are registered correctly, that is, how to offset them from one another to compensate for motion. This is particularly hard for Titan because visible-light pictures of the atmosphere have no sharp features to use as registration marks, and because the genuine orange-to-blue color gradient in the atmosphere's upper layers is hard to distinguish from a registration error. When making the above picture I could make the blue fringe considerably more or less prominent just by jogging the blue channel a few pixels. One thing I tried to go by was the appearance of the terminator near the horn of the crescent.
The publicly released color images from the Voyager spacecraft (even the ones not prominently identified as false-color) often had an exaggeratedly garish color balance. I think it's interesting to try to do better with the currently available technology; images with exaggerated color can be useful to bring out important features of the images, but it's also nice to try to get closer to a realistic you-are-there image once in a while.
To an outsider working from the JPL raw image archive, there are a number of uncertainties involved in putting these color pictures together. One is the question of whether the red, green and blue frames all had the same exposure settings. My experience with Cassini ISS camera images is that they're more likely to take roughly comparable exposures for the different color channels than, say, the Mars rover team is, so you can get pretty good color from a simple superimposition, but this is not always the case.
The other uncertainty is whether the frames are registered correctly, that is, how to offset them from one another to compensate for motion. This is particularly hard for Titan because visible-light pictures of the atmosphere have no sharp features to use as registration marks, and because the genuine orange-to-blue color gradient in the atmosphere's upper layers is hard to distinguish from a registration error. When making the above picture I could make the blue fringe considerably more or less prominent just by jogging the blue channel a few pixels. One thing I tried to go by was the appearance of the terminator near the horn of the crescent.
The publicly released color images from the Voyager spacecraft (even the ones not prominently identified as false-color) often had an exaggeratedly garish color balance. I think it's interesting to try to do better with the currently available technology; images with exaggerated color can be useful to bring out important features of the images, but it's also nice to try to get closer to a realistic you-are-there image once in a while.
Various bloggers have been asking and answering the question, "Which authors have you read more than ten books by?"
You can probably guess which ones are on my list because I talk about them a lot. They're pretty much all SF/fantasy authors (some write other things too). Off the top of my head:
Isaac Asimov
Arthur C. Clarke
Philip K. Dick
Stanislaw Lem
Terry Pratchett
Rudy Rucker
There are probably others. Most people who compile these lists seem to have many, many more ten-book authors than I do. I don't actually read a lot compared to people who read a lot.
I can think of many more who are probably somewhere in the seven-to-nine-book range. (I think that whether I've read ten books by Robert Heinlein depends on whether the full-length novels reprinted in The Past Through Tomorrow are counted separately.)
I'm not sure whether or not I read ten of Tove Jansson's Moomintroll books or Michael Bond's Paddington Bear books in my childhood. I think I've read eight or nine by C. S. Lewis. I don't think my relatively recent Gutenberg-fueled L. Frank Baum Oz project ever got to ten.
You can probably guess which ones are on my list because I talk about them a lot. They're pretty much all SF/fantasy authors (some write other things too). Off the top of my head:
Isaac Asimov
Arthur C. Clarke
Philip K. Dick
Stanislaw Lem
Terry Pratchett
Rudy Rucker
There are probably others. Most people who compile these lists seem to have many, many more ten-book authors than I do. I don't actually read a lot compared to people who read a lot.
I can think of many more who are probably somewhere in the seven-to-nine-book range. (I think that whether I've read ten books by Robert Heinlein depends on whether the full-length novels reprinted in The Past Through Tomorrow are counted separately.)
I'm not sure whether or not I read ten of Tove Jansson's Moomintroll books or Michael Bond's Paddington Bear books in my childhood. I think I've read eight or nine by C. S. Lewis. I don't think my relatively recent Gutenberg-fueled L. Frank Baum Oz project ever got to ten.