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Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Sun Jul 10, 2022 11:13 pm
by 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.
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Sun Jul 10, 2022 11:25 pm
by Chris Peterson
BillT wrote: ↑Sun Jul 10, 2022 11:13 pm
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.
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Mon Jul 11, 2022 1:58 am
by 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.
![Wink :wink:](./images/smilies/icon_wink.gif)
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Mon Jul 11, 2022 4:17 am
by Ann
Chris Peterson wrote: ↑Sun Jul 10, 2022 10:32 pm
Ann wrote: ↑Sun Jul 10, 2022 10:03 pm
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:
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
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Mon Jul 11, 2022 4:40 am
by Chris Peterson
Ann wrote: ↑Mon Jul 11, 2022 4:17 am
Chris Peterson wrote: ↑Sun Jul 10, 2022 10:32 pm
Ann wrote: ↑Sun Jul 10, 2022 10:03 pm
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.
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Mon Jul 11, 2022 5:47 am
by Ann
Chris Peterson wrote: ↑Mon Jul 11, 2022 4:40 am
Ann wrote: ↑Mon Jul 11, 2022 4:17 am
Chris Peterson wrote: ↑Sun Jul 10, 2022 10:32 pm
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.
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.
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
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Mon Jul 11, 2022 12:03 pm
by Chris Peterson
Ann wrote: ↑Mon Jul 11, 2022 5:47 am
Chris Peterson wrote: ↑Mon Jul 11, 2022 4:40 am
Ann wrote: ↑Mon Jul 11, 2022 4:17 am
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?
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Mon Jul 11, 2022 1:42 pm
by Ann
Chris Peterson wrote: ↑Mon Jul 11, 2022 12:03 pm
Ann wrote: ↑Mon Jul 11, 2022 5:47 am
Chris Peterson wrote: ↑Mon Jul 11, 2022 4:40 am
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
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Tue Jul 12, 2022 1:54 pm
by Chris Peterson
Ann wrote: ↑Mon Jul 11, 2022 1:42 pm
Chris Peterson wrote: ↑Mon Jul 11, 2022 12:03 pm
Ann wrote: ↑Mon Jul 11, 2022 5:47 am
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!
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Tue Jul 12, 2022 5:20 pm
by Ann
Chris Peterson wrote: ↑Tue Jul 12, 2022 1:54 pm
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
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Tue Jul 12, 2022 6:06 pm
by Chris Peterson
Ann wrote: ↑Tue Jul 12, 2022 5:20 pm
Chris Peterson wrote: ↑Tue Jul 12, 2022 1:54 pm
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!
_
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Tue Jul 12, 2022 6:11 pm
by VictorBorun
Ann wrote: ↑Mon Jul 11, 2022 5:47 am
But wavelengths are physics. Relative wavelengths are physics, too.
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.
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?
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Tue Jul 12, 2022 6:24 pm
by Ann
Chris Peterson wrote: ↑Tue Jul 12, 2022 6:06 pm
Ann wrote: ↑Tue Jul 12, 2022 5:20 pm
Chris Peterson wrote: ↑Tue Jul 12, 2022 1:54 pm
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!
_
Thanks, Chris, they are lovely!
![💙](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/1f499.svg)
![💜](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/1f49c.svg)
Ann
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Tue Jul 12, 2022 6:26 pm
by Chris Peterson
VictorBorun wrote: ↑Tue Jul 12, 2022 6:11 pm
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:
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Tue Jul 12, 2022 6:34 pm
by 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
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Tue Jul 12, 2022 6:38 pm
by johnnydeep
Ann wrote: ↑Tue Jul 12, 2022 6:34 pm
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!
Re: APOD: In the Center of the Cat's Eye Nebula (2022 Jul 10)
Posted: Wed Jul 13, 2022 6:26 pm
by MarkBour
Ann wrote: ↑Tue Jul 12, 2022 6:34 pm
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.