Chris Peterson wrote:Ann wrote:Well, that's me. Mapped color, when I can't "translate" it into true color, makes the object "unrelatable" to me.
There's no such thing as true color for dim astronomical objects. And you've never seen an image of an astronomical object that wasn't mapped color. So you'll need to be a good deal more precise in defining your terms if you want to be clearly understood.
Obviously, I mean the sort of color that can be seen by the "RGB" receptors in the human eye.
I am well aware of the fact that the human eye adapts to different ambient light and quickly adjusts its color reception accordingly. I still assume that it would be possible to find a way to create a standardized background light and measure how the human eye, adapted to this standardized background light, would typically perceive the color of different objects in space.
I am well aware that many objects in space are too faint for the human eye to perceive color in them. All right. I believe that there may be brighter objects of the same color, or rather of the same hue, and that it would be possible for humans to understand the hue of the fainter object by looking at the brighter object of the same hue.
Take galaxies. I believe that I understand the colors, and certainly the hues, of galaxies. The first time I saw the Andromeda galaxy at the age of fifteen, I had only seen a black and white picture of it, and I had no idea of what it would look like to my eye. It looked like soft yellowish patch of light. The yellowish color was very obvious. I saw it not because I was expecting it, but because I saw it. Many years later I spent a long time looking carefully through a telescope at the colors of bright stars of all spectral classes. I looked at very many different stars, and I also looked at many of the brightest stars over and over again. In the end, I felt confident that I really knew and could remember their colors.
Because I feel that I know the colors of stars, I also feel that I know the colors of galaxies. As I said, the Andromeda galaxy looked yellowish when I first saw it. Since then, I have seen very similar yellowish hues in, typically, K-type stars. I believe I can say that the overall color of the bulge of the Andromeda galaxy is very comparable to a K-type star.
Bright and moderately unreddened starforming regions, rich in O-type stars, can definitely be expected to look the same color as an unreddened O-type star. I have never seen the Large Magellanic Cloud or the fantastic star cluster R136, but I don't doubt that R136 is more or less the same color as an O-type star.
As for blue reflection nebulas, I think of them as extremely faint but even bluer in color than the stars whose light they reflect. I have seen the brighter members of the Pleiades many times, and I have often seen their blue color. Therefore I don't doubt that the reflection nebulas are even bluer than the bright blue stars themselves.
I also understand that the bright reflection nebula lit up by Antares should be yellow, since Antares emits copious amounts of yellow, orange and red light, but extremely little blue light.
As for Ha emission, I have most certainly never seen the color of it - and no one else has, either. I simply trust the RGB images of emission nebulas. They are very consistently shown as typically pink, which is the color you would expect from a lot of circa 656 nm Ha light mixed with a smaller quantity of circa 486 nm Hβ light. The sheer consistency of the pink color of emission nebulas in a very large number of RGB pictures made by many different photographers is convincing to me. Yes, I can understand that the pink color of emission nebulas may have become an established ideal, so that photographers might strive to make their RGB images of emission nebulas look pink simply because they feel that they
should look like that. I realize that that is a risk. But to me, the pink color makes such good sense in view of the wavelengths of Ha and Hβ light, that I simply accept it.
I find the OIII color frustrating and hard to picture. I have never seen it myself, and pictures, even RGB pictures, of planetary nebulas are not consistent. Some pictures show the OIII-bright parts of the planetaries as blue, some show them as aqua and some show them as green. To add to the confusion, a few planetaries look consistently blue in several pictures by different photographers. It is a complete mystery to me why a few planetaries should look decidedly bluer than others. Is their OIII light bluer than the other planetaries' OIII light?
And anyway, planetaries look so different in color pictures. Consider
this planetary, and
this, and
this, and
this, and
this, and
this, and
this. Why do their colors look so very different? How can I understand it?
Geckzilla would have told me that there is nothing to understand. The pictures show what they show and that's enough. I get that. I realize that these pictures are extremely valuable to people trying to understand the inner workings of planetary nebulas. I certainly don't protest when people are happy and excited when they look at pictures of planetaries similar to those I have just proved links to.
It is just that I see a cacophony of weird colors when I look at them.
Ann
A Halo for NGC 6164
