APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)

[BillT]

Doesn't require any experience. Everyone I have shown these two can see the the colour without any prompting. Even people who have never looked through a scope in their life before.

[Chris Peterson]

Doesn't require any experience. Everyone I have shown these two can see the the colour without any prompting. Even people who have never looked through a scope in their life before.

I don't know who you have shown, but very few people can see color in any deep sky objects.

[Fred the Cat]

A person could present the "Cat's Eye" in any medium and enjoy it but many may not think it representative.

The creativity that inspired it, is left for the eye of the beholder.

[Ann]

Easy. They are all gray.

Well, Chris, the day you have convinced me that all astronomical objects are gray, I'm outta here.

Seriously.

Ann

Just ask anybody who has ever observed deep sky objects directly.

Certainly, Chris.

Do I take it that you think that all astroimages should show only what the human eye can observe directly through a telescope?

Consider the APOD of July 11, 2022, and compare it with what a direct observation of the same object might look like:

Andromeda over the Sahara Desert. Credit & Copyright: Jordi Coy

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Wide field Andromeda. Image: tavaresjr.

Is it fair to show as much detail in Andromeda as we can see in today's APOD? When direct observation through a telescope may not reveal much more than what can be seen in tavaresjr's image?

Ann

[Chris Peterson]

Well, Chris, the day you have convinced me that all astronomical objects are gray, I'm outta here.

Seriously.

Ann

Just ask anybody who has ever observed deep sky objects directly.

Certainly, Chris.

Do I take it that you think that all astroimages should show only what the human eye can observe directly through a telescope?

No. But color loses most of its meaning when you are talking about things that the eye cannot perceive. Color is physiology, not physics.

[Ann]

Just ask anybody who has ever observed deep sky objects directly.

Certainly, Chris.

Do I take it that you think that all astroimages should show only what the human eye can observe directly through a telescope?

No. But color loses most of its meaning when you are talking about things that the eye cannot perceive. Color is physiology, not physics.

But wavelengths are physics. Relative wavelengths are physics, too.

Spitzer Space Telescope infrared image of M104. Shorter infrared wavelengths are mapped as blue, and longer infrared wavelenghts are mapped as red. Credit: NASA/JPL-Caltech.

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GALEX ultraviolet image of NGC 1512 and its small companion, NGC 1510. Shorter ultraviolet wavelengths are mapped as blue, and longer ultraviolet wavelengths are mapped as yellow. Credit: NASA/JPL-Caltech.

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In both Spitzer Space Telescope infrared images and GALEX ultraviolet images, shorter wavelengths were mapped as blue or cyan, and longer wavelengths were mapped as red or yellow. This makes perfect sense to me.

SDSS g-r-i image of NGC 2403. Green and blue wavelengths are mapped as blue, red wavelengths are mapped as green, and infrared wavelengths are mapped as red. Image: SDSS/Donald Pelletier.

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The Saturn Nebula. Credit and copyright: NASA/ESA/ Hubble Heritage Team.

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In SDSS g-r-i images of galaxies, green wavelengths are mapped as blue, red wavelengths are mapped as green and infrared wavelengths are mapped as red. Again shorter wavelengths are mapped as bluer hues and longer wavelengths are redder hues. Again, this makes perfect sense to me (and it has the consequence that red emission nebulas look green or cyan-colored in SDSS images, while individual cool stars tend to look very red).

But why does the Saturn Nebula look like that in a Hubble image? It makes no sense to me.

Ann

[Chris Peterson]

Certainly, Chris.

Do I take it that you think that all astroimages should show only what the human eye can observe directly through a telescope?

No. But color loses most of its meaning when you are talking about things that the eye cannot perceive. Color is physiology, not physics.

But wavelengths are physics. Relative wavelengths are physics, too.

Relative wavelengths are particularly irrelevant when we're considering narrow band images.

But why does the Saturn Nebula look like that in a Hubble image? It makes no sense to me.

I don't know why it makes no sense to you. Is it confusing that you say hej då and I say goodbye? Different sounds with the same meaning. Why is translating wavelengths to colors any different?

[Ann]

No. But color loses most of its meaning when you are talking about things that the eye cannot perceive. Color is physiology, not physics.

But wavelengths are physics. Relative wavelengths are physics, too.

Relative wavelengths are particularly irrelevant when we're considering narrow band images.

But why does the Saturn Nebula look like that in a Hubble image? It makes no sense to me.

I don't know why it makes no sense to you. Is it confusing that you say hej då and I say goodbye? Different sounds with the same meaning. Why is translating wavelengths to colors any different?

Perhaps we should say hej då and goodbye to this discussion, Chris?

You and I view color in the Universe in a fundamentally different way. To me color in astronomical objects is certainly a very subjective thing and a source of great joy, but it is also precise physical parameter. In the latter case, we are talking wavelengths, of course, not the conversion by the human eye and brain into the subjective sensation that we call color.

To me, color is hugely important, both when it comes to my own sense of aesthetics and when it comes to understanding the fundamental properties of an object through the wavelengths emitted or reflected by the object in question. To me, the color (or wavelength) of an astronomical object is no more trivial than the size, mass or shape of the object.

I'm sure you know that. And you don't agree with me. So let's agree to disagree. I'll keep claiming that an APOD portrait of an object gives us a good, or a misleading, idea of what the object's "natural", or optical, or visual, color is. And you are going to tell everyone here that I'm talking nonsense.

That's okay. You and I disagree on color. Let's leave it at that and say hej då and goodbye, until there is another APOD whose "color portrait" of an object prompts me to explain the properties of the object from its ("true") color.

Ann

[Chris Peterson]

But wavelengths are physics. Relative wavelengths are physics, too.

Relative wavelengths are particularly irrelevant when we're considering narrow band images.

But why does the Saturn Nebula look like that in a Hubble image? It makes no sense to me.

I don't know why it makes no sense to you. Is it confusing that you say hej då and I say goodbye? Different sounds with the same meaning. Why is translating wavelengths to colors any different?

Perhaps we should say hej då and goodbye to this discussion, Chris?

You and I view color in the Universe in a fundamentally different way. To me color in astronomical objects is certainly a very subjective thing and a source of great joy, but it is also precise physical parameter. In the latter case, we are talking wavelengths, of course, not the conversion by the human eye and brain into the subjective sensation that we call color.

To me, color is hugely important, both when it comes to my own sense of aesthetics and when it comes to understanding the fundamental properties of an object through the wavelengths emitted or reflected by the object in question. To me, the color (or wavelength) of an astronomical object is no more trivial than the size, mass or shape of the object.

I'm sure you know that. And you don't agree with me. So let's agree to disagree. I'll keep claiming that an APOD portrait of an object gives us a good, or a misleading, idea of what the object's "natural", or optical, or visual, color is. And you are going to tell everyone here that I'm talking nonsense.

That's okay. You and I disagree on color. Let's leave it at that and say hej då and goodbye, until there is another APOD whose "color portrait" of an object prompts me to explain the properties of the object from its ("true") color.

Ann

I don't disagree with that much. But I will not agree to agree with you calling any color scheme "wrong". Because that is wrong, and I'll call you out every time!

[Ann]

I don't disagree with that much. But I will not agree to agree with you calling any color scheme "wrong". Because that is wrong, and I'll call you out every time!

Do that, Chris, because the word "wrong" is particularly useless as a description of color in astronomical objects. The adjective is provocative and annoying, but practically devoid of all precise information.

Ann

[Chris Peterson]

I don't disagree with that much. But I will not agree to agree with you calling any color scheme "wrong". Because that is wrong, and I'll call you out every time!

Do that, Chris, because the word "wrong" is particularly useless as a description of color in astronomical objects. The adjective is provocative and annoying, but practically devoid of all precise information.

Ann

Well, speaking of color, I'm sure you'll appreciate this, taken at 3700 meters on a hike yesterday. Chiming Bells and Columbine. There were blue wildflowers everywhere. Nothing wrong about these colors!
_

[VictorBorun]

But wavelengths are physics. Relative wavelengths are physics, too.

Spitzer Space Telescope infrared image of M104. Shorter infrared wavelengths are mapped as blue, and longer infrared wavelenghts are mapped as red. Credit: NASA/JPL-Caltech.

---

GALEX ultraviolet image of NGC 1512 and its small companion, NGC 1510. Shorter ultraviolet wavelengths are mapped as blue, and longer ultraviolet wavelengths are mapped as yellow. Credit: NASA/JPL-Caltech.

---

In both Spitzer Space Telescope infrared images and GALEX ultraviolet images, shorter wavelengths were mapped as blue or cyan, and longer wavelengths were mapped as red or yellow. This makes perfect sense to me.

SDSS g-r-i image of NGC 2403. Green and blue wavelengths are mapped as blue, red wavelengths are mapped as green, and infrared wavelengths are mapped as red. Image: SDSS/Donald Pelletier.

---

The Saturn Nebula. Credit and copyright: NASA/ESA/ Hubble Heritage Team.

---

In SDSS g-r-i images of galaxies, green wavelengths are mapped as blue, red wavelengths are mapped as green and infrared wavelengths are mapped as red. Again shorter wavelengths are mapped as bluer hues and longer wavelengths are redder hues. Again, this makes perfect sense to me (and it has the consequence that red emission nebulas look green or cyan-colored in SDSS images, while individual cool stars tend to look very red).

But why does the Saturn Nebula look like that in a Hubble image? It makes no sense to me.
Ann

Here come new images from Webb, with its wild wide band, far IR having 10 times lower resolution than near IR.
To fully use human vision, we should encode the longest waves in blue sub-pixels of an RGB picture.
To preserve the monotony even if takes to inverse it we should encode the shortest waves in red.
It would take time to get used to that legend where hot is red and cold is blue (and halfway warm-cool is not gray, but rather green), but what other way is there?

[Ann]

I don't disagree with that much. But I will not agree to agree with you calling any color scheme "wrong". Because that is wrong, and I'll call you out every time!

Do that, Chris, because the word "wrong" is particularly useless as a description of color in astronomical objects. The adjective is provocative and annoying, but practically devoid of all precise information.

Ann

Well, speaking of color, I'm sure you'll appreciate this, taken at 3700 meters on a hike yesterday. Chiming Bells and Columbine. There were blue wildflowers everywhere. Nothing wrong about these colors!
_

Click to view full size image

Thanks, Chris, they are lovely!

Ann

[Chris Peterson]

To preserve the monotony even if takes to inverse it we should encode the shortest waves in red.

Monotonicity, please! Monotony is very different, and not to be found in the JWST images. :lol2:

[Ann]

Got to show you perhaps the most beautiful picture I have seen, fittingly called "The Blue Universe" by Japanese photographer Hiroki Kondo:

Amazing, isn't it?

National Geographic wrote:
THE BLUE UNIVERSE

About 4.5 million Nemophila menziesii—a California wildflower commonly known as baby blue eyes—carpet the hills at Hitachi Seaside Park in Japan. According to photographer Hiroki Kondo, who calls this landscape “the blue universe,” the flowers peak from the end of April to the first week of May.

Amazing, isn't it? Sigh! Sometimes we can see heaven on Earth. Or - wait! I take that back! Sometimes we can really see that the Earth is the heaven of the Universe. At the very least, it sure looks like it sometimes!

Ann

[johnnydeep]

Got to show you perhaps the most beautiful picture I have seen, fittingly called "The Blue Universe" by Japanese photographer Hiroki Kondo:

A blue universe in Japan Hiroki Kondo.png

Amazing, isn't it?

National Geographic wrote:
THE BLUE UNIVERSE

About 4.5 million Nemophila menziesii—a California wildflower commonly known as baby blue eyes—carpet the hills at Hitachi Seaside Park in Japan. According to photographer Hiroki Kondo, who calls this landscape “the blue universe,” the flowers peak from the end of April to the first week of May.

Amazing, isn't it? Sigh! Sometimes we can see heaven on Earth. Or - wait! I take that back! Sometimes we can really see that the Earth is the heaven of the Universe. At the very least, it sure looks like it sometimes!

Ann

Nice. All that's missing is a stretch of nice blue ocean between earth and sea!

[MarkBour]

Got to show you perhaps the most beautiful picture I have seen, fittingly called "The Blue Universe" by Japanese photographer Hiroki Kondo:
...
Amazing, isn't it? Sigh! Sometimes we can see heaven on Earth. Or - wait! I take that back! Sometimes we can really see that the Earth is the heaven of the Universe. At the very least, it sure looks like it sometimes!

Ann

Nice! I especially like the color in the shade of the tree.
It is nice of the Japanese to allow these Californians to flourish.