Starship Asterisk*

Ann wrote:

Anthony Barreiro wrote:
I wonder if that's why the blue reflection nebulae stand out in clear contrast in this image?

There are no blue reflection nebulae visible in this image. The small bluish areas in this image get their color from OIII emission due to strong ultraviolet emission from very hot stars.

The reason why the bluish areas are so small is likely twofold. It seems very probable that the Heart Nebula contains considerably more Ha than OIII emission. However, it was also the choice of the person processing the image not to emphasize the OIII emission and therefore "keep down" the blue channel. Another Hubble Palette image of the Heart Nebula shows a lot of blue, but again that must have been the choice of the person doing the processing.

In any case, the blue areas in the Heart Nebula could not have been reflection nebulae. OIII emission is only found in rarefied, "empty" areas near energetic stars or near "energetic events" such as supernova remnants, whereas (blue) reflection nebulae are always found in dusty areas.

Ann

Anthony Barreiro wrote:
I wonder if that's why the blue reflection nebulae stand out in clear contrast in this image?

Chris Peterson wrote:Color theory is very complex. Consider just the simple fact that we may perceive identical colors created by a single narrow emission line or a rich mixture of wavelengths across the spectrum. Consider that we perceive a particular hue as different colors depending on intensity. The thing that distinguishes orange and brown, for example, is intensity, nothing else.

The sensors in our eyes don't correspond very closely with the red, green, and blue primaries of our monitors, nor with the cyan, magenta, and yellow of our subtractive color systems. So displayed colors, printed colors, and the colors we perceive all occupy different mathematical spaces. Converting between them is non-trivial (and there are many things that can't be converted perfectly- for instance, it is impossible to duplicate pure red in the standard additive system used by monitors using the CMY system of printing.

Anthony Barreiro wrote:I've been thinking about the question of creating colors by combining red, green, and blue light. Is this purely a technical issue for people who are creating digital images or television pictures, or is this analogous to what happens in nature? I think of the light that comes from the Sun or another star as having a continuous spectrum of all the colors of the rainbow, with interesting dark lines where specific wavelengths of light are absorbed by elements or molecules in the star's cooler outer layers. An emission nebula or a reflection nebula would have a much narrower spectrum, but it would be centered on a specific wavelength corresponding to a specific color, right? Am I missing something?

neufer wrote:The brown and orange disks of color are objectively identical, in identical gray surrounds, in this image; their perceived color categories depend on what white they are compared to.

Chris Peterson wrote:
... the light areas are substantially unsaturated. They're similar in color and intensity to what we'd see with a redder palette, as well. At that point color is just a cast. The brightest areas in any image tend to be white.

geckzilla wrote:
<<That's what brown traditionally is, though. It's a special name we have for a desaturated zone of red and orange. It's the only desaturated color we have that is considered discreet. All others are recognized as pastel or drab versions of their saturated basic colors. It's very interesting to me that this happened. If you explain this to someone unfamiliar with color they will be incredulous that brown is related to red or orange at all.

I agree your 128,64,0 brown is brown but it is an exceptional and mathematically ideal state of brown that is at once saturated and yet still looks brown even against a black background instead of dark orange or dark yellow.>>

geckzilla wrote:Your definition is fine for the dark areas but at medium and lighter values brown (or tan, if you prefer) is no longer brown without blue. It's not crucial in some sense but it's necessary for natural looking browns and other subtle variations. Turning off the blue channel shifts it terribly yellow as one would expect so I disagree with you on that last statement.

geckzilla wrote:

Chris Peterson wrote:I'd say brown requires two channels- red and green. Brown is low intensity orange, so you have about twice as much red as green, and no blue.

How do you propose to bring the intensity of that orange down without blue?

Chris Peterson wrote:I'd say brown requires two channels- red and green. Brown is low intensity orange, so you have about twice as much red as green, and no blue.

Chris Peterson wrote:I'd say brown requires two channels- red and green. Brown is low intensity orange, so you have about twice as much red as green, and no blue.

Chris Peterson wrote:Low to middle saturation reds and pinks tend to use high levels of all three primaries. In most cases, you have more photons coming off the screen with pink than brown.

I think the greater apparent dynamic range has more to do with how the light and dark points are set with browns than with absolute intensity.

geckzilla wrote:

Anthony Barreiro wrote:The more pictures of nebulae I see in shades of brown, the more I like that palette. Somehow I find it easier to see depth and structure in brown clouds than pink clouds. (And I don't know if I could stomach a pink apod on Valentine's day! )

That's because it takes all three color channels to create brown, which means you've got more photons being sent to your eyes. It's much brighter than red alone, which requires green and blue to be significantly subdued to look vibrant and red. Despite being darker, red tends to be more eye-catching. It's an aesthetic trade-off either way.

geckzilla wrote:

Anthony Barreiro wrote:The more pictures of nebulae I see in shades of brown, the more I like that palette. Somehow I find it easier to see depth and structure in brown clouds than pink clouds. (And I don't know if I could stomach a pink apod on Valentine's day! :lol2: )

That's because it takes all three color channels to create brown, which means you've got more photons being sent to your eyes. It's much brighter than red alone, which requires green and blue to be significantly subdued to look vibrant and red. Despite being darker, red tends to be more eye-catching. It's an aesthetic trade-off either way.

Anthony Barreiro wrote:The more pictures of nebulae I see in shades of brown, the more I like that palette. Somehow I find it easier to see depth and structure in brown clouds than pink clouds. (And I don't know if I could stomach a pink apod on Valentine's day! )

Mactavish wrote:

FloridaMike wrote:

jsanchezjr wrote:.... we also know without a doubt how is our galaxy when we can watched from the outside, sure, if ever possible.

Yes, we are awaiting the return of V'ger to confirm this.

I don’t think I’ll wait up for that to happen, but I’ll leave a light on anyway.

FloridaMike wrote:

jsanchezjr wrote:.... we also know without a doubt how is our galaxy when we can watched from the outside, sure, if ever possible.

Yes, we are awaiting the return of V'ger to confirm this.

jsanchezjr wrote:.... we also know without a doubt how is our galaxy when we can watched from the outside, sure, if ever possible.

Chris Peterson wrote:

jsanchezjr wrote:Beautiful image for those who celebrate the festivity(there are those who don't celebrate it, like myself, for having a pagan origin with a beginning in a pre-Roman celebration call it 'Lupercalia') but something that interested me was the link 'spiral arm' that explain the theory of the two spiral arms of our galaxy. I call it theory because, I think, the truth is that to know exactly how is our galaxy, first we should be out of it to view it from the outside. And I'm afraid that this will take a long time to achieve.

While it's truly a theory, it's one which is very well supported by observational evidence. You don't have to outside the galaxy to make excellent measurements of its structure. With radio and IR we can see great distances, and there are methods of estimating the distance to stars and other structures. If you know the coordinates and the distance, you can make a structural model.

That the Milky Way is a spiral galaxy is known beyond reasonable doubt. The details still being worked out have to do with whether there are two or four arms, whether there's a bar, and the like. These things can be tricky to decide even when looking at other galaxies.

jsanchezjr wrote:Beautiful image for those who celebrate the festivity(there are those who don't celebrate it, like myself, for having a pagan origin with a beginning in a pre-Roman celebration call it 'Lupercalia') but something that interested me was the link 'spiral arm' that explain the theory of the two spiral arms of our galaxy. I call it theory because, I think, the truth is that to know exactly how is our galaxy, first we should be out of it to view it from the outside. And I'm afraid that this will take a long time to achieve.

Chris Peterson wrote:Well, to a degree. But beyond a certain point- and it's not very large (well under a meter), aperture isn't usually about higher resolution, but about greater light collecting ability. The TMT isn't going to provide any higher resolution for wide angle shots than amateurs are getting every day. Large telescopes in space can do that, but not on the ground. Future images made from the ground won't be any more zoomable than existing images.