1. Nasif: "But ultimately a red giant, Cat's Eye Nebula, is obviosly red, even if we see black and white."
Dude, a red giant isn't RED, what part of the following did you not understand?
On a more popular note, Brecher suggests the very vocabulary of astronomy is riddled with misleading color terms. Red giant stars like the bright and popular Betelgeuse, for example, are not really red, though they can sometimes appear so from Earth.
"If you could walk up to Betelgeuse, it would look white," he says.
That's because the star's light would overwhelm the color-sensing cones in your eyes. Only from a great distance, when the star is relatively dim, can the cones sometimes detect a hint of red. The vast majority of red giants, however, set off only the rods in your eyes, which cannot detect color at all. So most stars appear white, regardless of how they are classified.
2. And what point did you want to prove with the RGB composition link from the hubble site? Let's read some of the stuff from the very site you gave me.
a. Representative color helps scientists visualize what would otherwise be invisible, such as the appearance of an object in infrared light.
b. Enhancing the visible colors in an image often brings out an object's subtle structural detail.
c. We use color:
• To depict how an object might look to us if our eyes were as powerful as Hubble
• To visualize features of an object that would ordinarily be invisible to the human eye
• To bring out an object's subtle details.
Color in Hubble images is used to highlight interesting features of the celestial object being studied. It is added to the separate black-and-white exposures that are combined to make the final image.
Creating color images out of the original black-and-white exposures is equal parts art and science.
Which is exactly my point.
And you know what's funny? The example of this art of color doctoring they give us is none other than your cat's eye nebula. haha!
3. This is how it's done, again, taken from the very site you gave me:
Taking color pictures with the Hubble Space Telescope is much more complex than taking color pictures with a traditional camera. For one thing, Hubble doesn't use color film — in fact, it doesn't use film at all. Rather, its cameras record light from the universe with special electronic detectors.
These detectors produce images of the cosmos not in color, but in shades of black and white.
Finished color images are actually combinations of two or more black-and-white exposures to which color has been added during image processing.
The colors in Hubble images, which are assigned for various reasons, aren't always what we'd see if we were able to visit the imaged objects in a spacecraft. We often use color as a tool, whether it is to enhance an object's detail or to visualize what ordinarily could never be seen by the human eye.
There is NO RGB detector in hubble! Where did you find that info? Did you just make that up? There are, however, RGB manipulation techniques that scientists use on these black and white photos to 1. enhance technical details 2. visual pleasure. Let's say, hypothetically, they wanna measure the intensity of light in the photo. Instead of using just brightness as a measure they use the color red. The more intense a part, the redder it is. The less intense, more pinkish it becomes. But it doesn't REALLY mean that the thing is red! The color is used to aid our understanding. And scientists may use different colors for the same property they wanna highlight in different photos. Maybe in other photos, intensity was shown with blue color. It's COMPLETELY ARBITRARY and SUBJECTIVE to the Color Enhancing Person's personal artistic choice.
So my question is:
Why do you say there is an optical RGB detector in Hubble when there is none? Why are you bent on bending the truth? Is your faith SO strong that you have to brainwash yourself like that?
Here's what happened when they were producing your famous pic. First they took an x-ray pic from Chandra observatory of the nebula. (This is the pic on the left of yourpost) Now I don't know about you, but X-rays don't have orange color. WE CAN'T EVEN SEE X-RAYS! They ADDED that color so that we can get a FEEL for what's happening.
And then they took two images from hubble, which were initially BLACK-and- WHITE images ALREADY color-doctored with red and green.
Notice how the chandra image on the left all on a sudden was converted from orange to blue in the composite pic on the right.
That's because they wanted to compare the "hotness" of different parts of the nebula. But OUR HUMAN EYES are NOT capable of seeing such stuff. So they color coded the hotness with more hot being red and less hot being blue.
It's ALL subjective. They could have easily color coded hot being green and cold being red.
It's color doctoring. As simple as that.
[Edited on 21-11-2003 by Arnab]
[Edited on 21-11-2003 by Arnab]