APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 17)

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Expand view Topic review: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 17)

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Beyond » Wed Feb 19, 2014 3:06 am

Yeah, i was wondering about that. Guess we'll have to wait till someone who actually knows Spanish can say how good the machine translation is.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by geckzilla » Wed Feb 19, 2014 2:38 am

I wouldn't trust a machine translator to convey something like this that can be easily confused or I would have done it myself.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Beyond » Wed Feb 19, 2014 12:48 am

geckzilla wrote:They're wondering about the black dots in the centers of stars. If anyone can translate this to Spanish say it's just where the CCD is saturated. It got so bright that it turned black.
For what it's worth... here's the BING translation into Spanish = Si alguien puede traducir esto al español decir es sólo donde el CCD está saturado. Fue tan brillante que resultó ser negro.

And here is the translation of that translation, back into English = If someone can translate this to the Spanish say is only where the CCD is saturated. It was so bright that it turned out to be black.

So it looks like BING did a decent job of translating.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by geckzilla » Wed Feb 19, 2014 12:37 am

They're wondering about the black dots in the centers of stars. If anyone can translate this to Spanish say it's just where the CCD is saturated. It got so bright that it turned black.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Beyond » Wed Feb 19, 2014 12:32 am

Elpatriarcasandokan wrote:In Spanish : Al acercarme se ven algunos discos con puntos en la mitad ?????
???????? ........ ?




?
BING Translator= To bring me some discs are points in half
I say... ??????????????

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Elpatriarcasandokan » Tue Feb 18, 2014 11:56 pm

In Spanish : Al acercarme se ven algunos discos con puntos en la mitad ?????
???????? ........ ?




?

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by RJN » Tue Feb 18, 2014 1:32 am

Ann wrote: The colors in this image are somewhat muted, and the blue channel has not been given a boost. NGC 2070 is located nearly dead center of the image. Anyone looking for blue stars on the right of this picture will look in vain.
Thanks Ann! Fixed it. - RJN

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Chris Peterson » Mon Feb 17, 2014 10:18 pm

Ron-Astro Pharmacist wrote:Is the mechanism that causes star formation from a supernova known?

One might think that energy being released from a supernova explosion would drive the gravitationally attracted material apart rather than causing it to aggregate more vigorously. :?:
Most of the parent material is driven apart (but not all). But where fast material interacts with other material, you get shock fronts, where gas and dust pile up. Those concentrations are one of the things that can seed new star formation.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Ron-Astro Pharmacist » Mon Feb 17, 2014 10:10 pm

Is the mechanism that causes star formation from a supernova known?

One might think that energy being released from a supernova explosion would drive the gravitationally attracted material apart rather than causing it to aggregate more vigorously. :?:

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Chris Peterson » Mon Feb 17, 2014 8:46 pm

geckzilla wrote:Lab confuses me. I use HSL (It is called HSB in PS) for my color sliders, though. That is a very sensible way to represent color. Munsell called it hue, chroma, and value. Apparently chroma and saturation aren't the same thing, though... I guess I have failed at making such a distinction for a long time.
LAB can be confusing, but it's nearly ideal for working with astronomical images. It allows you to apply transfer functions (curves) without changing the size of stars across RGB channels, and to use filters like sharpening and blurring without creating colored halos. Try playing around with it. Convert to LAB to apply any filters and curves, then shift back to RGB to work more naturally with color balance (which should be subtle at that point).

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by geckzilla » Mon Feb 17, 2014 8:35 pm

Chris Peterson wrote:
geckzilla wrote:Looking at the blue channel alone the stars are spread out much larger than the green and red and detail has been lost in the central nebula where it has become pure white.

Edit: This is not to say that this is somehow wrong. I think it's fairly typical and I've done it a lot myself.
I wouldn't choose the word "overexposed" for this. But certainly, the blue channel has had its intensity stretched more than the other two channels, with the result that the bright stars in the blue channel have been bloated. This results in blue halos around the stars in the full color image.

I like to work in LAB or HSL color spaces when processing astronomical images, because it largely prevents this kind of distortion.
Lab confuses me. I use HSL (It is called HSB in PS) for my color sliders, though. That is a very sensible way to represent color. Munsell called it hue, chroma, and value. Apparently chroma and saturation aren't the same thing, though... I guess I have failed at making such a distinction for a long time.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by geckzilla » Mon Feb 17, 2014 8:28 pm

rgendler wrote:I like your version. The color balance is now much improved. BTW I wasn't trying to be critical of Damian's fine image. Anyone who does serious astronomical image processing knows the benefit of another pair of fresh eyes.
Too true... many times have I come back to an image after not looking at it for a week or at least a couple of days so I can look at it with fresh eyes, myself. I have nightmares about my vision somehow being reduced and having to rely on the color picker tool to see for me...I guess that would reduce that bias that forms after staring at an image for hours on end. Nothing like grabbing the color picker and realizing what you thought was one color was actually not that color at all.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by rgendler » Mon Feb 17, 2014 8:15 pm

geckzilla wrote:
Ann wrote:The colors in this image are somewhat muted, and the blue channel has not been given a boost.
Blue is actually quite overexposed in this image. To me, this picture is quite colorful--the opposite of muted. I'm not sure how you could say that it's muted.
rgendler wrote:Strictly from an image processing perspective the entire image is shift towards red. Even the blue stars are shifted towards purple which confirms my suspicion. This was done I'm sure to maximally enhance the tendrils of emission nebulosity abundant throughout the field. I would bet that dropping the mid-level of the red channel using curves would improve the overall color balance tremendously.
I agree, it's very red. I would suggest some changes to be made using Photoshop's channel mixer rather than the curves. We can take the purple out of the blues by changing the red output. Modifying its input to take +30% from the green channel and -30% from the blue channel is sufficient. This will avoid sacrificing brightness. To reduce the pinkness of the nebula we can then adjust the green output by modifying its input to +10% red channel and +90% green channel. The result should look like this.

I should note that I don't find any fault with Damian's original work, personally. Purple is my favorite color, anyway. I may have done it differently if I had done it but I enjoy Damian's version a lot. I recognize that even though the stars appear purple absolutely, relatively they are bluer than the nebula and that is sufficient for my brain to interpret the stars as being bluer.

I like your version. The color balance is now much improved. BTW I wasn't trying to be critical of Damian's fine image. Anyone who does serious astronomical image processing knows the benefit of another pair of fresh eyes.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Chris Peterson » Mon Feb 17, 2014 8:11 pm

geckzilla wrote:Looking at the blue channel alone the stars are spread out much larger than the green and red and detail has been lost in the central nebula where it has become pure white.

Edit: This is not to say that this is somehow wrong. I think it's fairly typical and I've done it a lot myself.
I wouldn't choose the word "overexposed" for this. But certainly, the blue channel has had its intensity stretched more than the other two channels, with the result that the bright stars in the blue channel have been bloated. This results in blue halos around the stars in the full color image.

I like to work in LAB or HSL color spaces when processing astronomical images, because it largely prevents this kind of distortion.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by geckzilla » Mon Feb 17, 2014 8:05 pm

Ann wrote:
Geckzilla wrote:
Blue is actually quite overexposed in this image.
Really? You mean that blue is overexposed to the point that it looks whitish?
Looking at the blue channel alone the stars are spread out much larger than the green and red and detail has been lost in the central nebula where it has become pure white.

Edit: This is not to say that this is somehow wrong. I think it's fairly typical and I've done it a lot myself.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Ann » Mon Feb 17, 2014 7:59 pm

Geckzilla wrote:
Blue is actually quite overexposed in this image.
Really? You mean that blue is overexposed to the point that it looks whitish?

Ann

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Chris Peterson » Mon Feb 17, 2014 7:38 pm

Spif wrote:Those damned arthropods, they seem to get everywhere.

Fortunately, we've recently been getting better at making really huge lasers.
The smart arthropods are just going to admonish us, "Be careful or you'll put your eyes out with that thing!" And they'll probably be right.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by HunterofPhotons » Mon Feb 17, 2014 7:37 pm

It would have been nice if he had fixed the blooms on the bright stars and backed off on the sharpening a bit as the brighter stars have the doughnut profile of over-sharpened stars.

dan k.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Beyond » Mon Feb 17, 2014 7:32 pm

Spif wrote:
Nitpicker wrote: How hospitable do you want it to be? I imagine that if our world were much more hospitable to life, we might have been wiped out by a superior species of arthropod.
Those damned arthropods, they seem to get everywhere.

Fortunately, we've recently been getting better at making really huge lasers.
Now if they can just figure a way to get those arthropods to the focal point of that really big laser.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Spif » Mon Feb 17, 2014 7:24 pm

Ann wrote:
Still, I have to wonder if it is better for life to be inside a much, much quieter galaxy. How about NGC 205, one of the obvious satellite galaxies of the Andromeda Galaxy, here photographed by Adam Block? Would that galaxy offer living organisms more hospitable conditions than the Large Magellanic Cloud can do?
As I understand it, the LMC is an irregular galaxy because it is being gravitationally perturbed by proximity to our own galaxy. These perturbations are provoking compressions of the cold matter clouds inside the galaxy, giving rise to the huge star forming zones.

I believe those areas would not be good places for life to form for a while because all the new short-lived stars keep exploding throughout the region. Once the perturbations stop or the clouds dissipate, the huge blue stars will die off and leave a quiet zone with only the smaller, longer-lived stars behind (like our sun).

But I believe that being in close proximity to the Milky Way, the LMC is going to continue getting warped and twisted by gravitational tidal forces on each new orbit.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Spif » Mon Feb 17, 2014 7:11 pm

Nitpicker wrote: How hospitable do you want it to be? I imagine that if our world were much more hospitable to life, we might have been wiped out by a superior species of arthropod.
Those damned arthropods, they seem to get everywhere.

Fortunately, we've recently been getting better at making really huge lasers.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by geckzilla » Mon Feb 17, 2014 7:08 pm

Ann wrote:The colors in this image are somewhat muted, and the blue channel has not been given a boost.
Blue is actually quite overexposed in this image. To me, this picture is quite colorful--the opposite of muted. I'm not sure how you could say that it's muted.
rgendler wrote:Strictly from an image processing perspective the entire image is shift towards red. Even the blue stars are shifted towards purple which confirms my suspicion. This was done I'm sure to maximally enhance the tendrils of emission nebulosity abundant throughout the field. I would bet that dropping the mid-level of the red channel using curves would improve the overall color balance tremendously.
I agree, it's very red. I would suggest some changes to be made using Photoshop's channel mixer rather than the curves. We can take the purple out of the blues by changing the red output. Modifying its input to take +30% from the green channel and -30% from the blue channel is sufficient. This will avoid sacrificing brightness. To reduce the pinkness of the nebula we can then adjust the green output by modifying its input to +10% red channel and +90% green channel. The result should look like this.

I should note that I don't find any fault with Damian's original work, personally. Purple is my favorite color, anyway. I may have done it differently if I had done it but I enjoy Damian's version a lot. I recognize that even though the stars appear purple absolutely, relatively they are bluer than the nebula and that is sufficient for my brain to interpret the stars as being bluer.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Anthony Barreiro » Mon Feb 17, 2014 6:30 pm

The caption's comparison of the sizes of the Tarantula and Orion nebulas prompted me to look them up. According to sky safari 4:

Object .............. Distance ............... Diameter ........... Apparent size ........ Visual magnitude

Tarantula ..... 160,000 light years ..... 1833 light years ..... 40 x 25 arcminutes ..... 5

Orion ............. 1,400 light years ....... 35 light years ...... 85 x 60 arcminutes ..... 4

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Chris Peterson » Mon Feb 17, 2014 6:13 pm

rgendler wrote:I would bet that dropping the mid-level of the red channel using curves would improve the overall color balance tremendously.
That is, of course, an aesthetic viewpoint. Certainly, it would change the color balance. Since there's really no such thing as truly accurate color with objects like this (outside of the stars, perhaps), it becomes a matter of taste. Personally, I like more muted colors (but then, I generally prefer B&W astroimages to color, so that's not too surprising). What I tend to dislike the most is highly saturated colors. If I were processing this, I'd decrease the saturation still more, and bring up the brightness a little in the midtones.

So many ways of visualizing things. That's why we can keep viewing the same objects over and over again in forums like this, and always discover new ways of seeing them.

Re: APOD: The Cosmic Web of the Tarantula Nebula (2014 Feb 1

by Anthony Barreiro » Mon Feb 17, 2014 5:59 pm

jsanchezjr wrote:
apod robot wrote: Since massive stars live fast and die young, it is not so surprising that the cosmic Tarantula also lies near the site of a close recent supernova.
Thinking about that. We all know that when all the fuel is gone a star begin to die and at the final stage end like a white dwarf, neutron star, black hole etc. But if a star have a endless fuel to preserve a continous fusion on its core? Easy, the star never die. My point is that the most abundant element in the universe is precisely hydrogen, the fuel of the stars. So, if some how, some way, our star is continuously receiving hydrogen, well, it never die, we can call it everlasting. And in consequent our precios planet can have a everlasting live too. For me is not a crazy idea, is a logic one. We only need some one that can do that or teach us how to do it...
That's an interesting idea, Jose. Of course you would have to find massive quantities of hydrogen and transport them to the Sun. Since hydrogen fusion happens in the core of a star, under tremendous pressure and temperature, you would have to figure out how to get fresh hydrogen into the Sun's core, overcoming the great outward pressure generated by the energy released by the fusion that's already happening.

To my way of thinking, it is a fundamental truth that nothing lasts forever. Just ask any of the species diappearing during Earth's sixth mass extinction. I find a certain tragic beauty in the fact that the biggest, brightest stars lead the shortest lives, and die most spectacularly.

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