Comments and questions about the
APOD on the main view screen.
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Ann
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by Ann » Mon Apr 10, 2023 5:39 am
Running Chicken Nebula annotated O Donnell.png
The Running Chicken Nebula. Credit: Dylan O'Donnell.
I think today's APOD is quite nice. I'm often unenthusiastic about mapped color narrowband images, but this one looks good. Of course, I object to the caption's claim that the colors of the APOD have been scientifically assigned. There is nothing scientific about them. They were just chosen to look good, and yes, they do look quite good.
The Running Chicken Nebula is known for its Bok globules (or Thackaray globules). The caption of the images reads:
ESO wrote:
This intriguing new view of a spectacular stellar nursery IC 2944 is being released to celebrate a milestone: 15 years of ESO’s Very Large Telescope. This image also shows a group of thick clouds of dust known as the Thackeray globules silhouetted against the pale pink glowing gas of the nebula. These globules are under fierce bombardment from the ultraviolet radiation from nearby hot young stars. They are both being eroded away and also fragmenting, rather like
lumps of butter dropped onto a hot frying pan. It is likely that Thackeray’s globules will be destroyed before they can collapse and form new stars.
Ann
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alex555
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by alex555 » Mon Apr 10, 2023 8:00 am
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De58te
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by De58te » Mon Apr 10, 2023 1:03 pm
Ahh! Thanks Ann and Dylan for the outline. I was wondering why it looks like a running chicken. Apparently the head of the chicken has been cut off from the main nebula body. At first I thought the head was at the bottom right and the head with the bright star for eyes looked more like a vulture's or turkey head, and the vulture was flying.
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Chris Peterson
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by Chris Peterson » Mon Apr 10, 2023 1:44 pm
Ann wrote: ↑Mon Apr 10, 2023 5:39 am
Of course, I object to the caption's claim that the colors of the APOD have been scientifically assigned. There is nothing scientific about them. They were just chosen to look good, and yes, they do look quite good.
I don't know if they're scientifically assigned or not. My objection is that there is no information about this image to be found, so it's essentially useless for anything other than admiring pretty colors. Not an image that should be accepted for APOD, IMO.
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Ann
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by Ann » Mon Apr 10, 2023 3:00 pm
Chris Peterson wrote: ↑Mon Apr 10, 2023 1:44 pm
Ann wrote: ↑Mon Apr 10, 2023 5:39 am
Of course, I object to the caption's claim that the colors of the APOD have been scientifically assigned. There is nothing scientific about them. They were just chosen to look good, and yes, they do look quite good.
I don't know if they're scientifically assigned or not. My objection is that there is no information about this image to be found, so it's essentially useless for anything other than admiring pretty colors. Not an image that should be accepted for APOD, IMO.
Chris, how do you assign scientific colors to a narrowband image?
Ann
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Chris Peterson
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by Chris Peterson » Mon Apr 10, 2023 3:06 pm
Ann wrote: ↑Mon Apr 10, 2023 3:00 pm
Chris Peterson wrote: ↑Mon Apr 10, 2023 1:44 pm
Ann wrote: ↑Mon Apr 10, 2023 5:39 am
Of course, I object to the caption's claim that the colors of the APOD have been scientifically assigned. There is nothing scientific about them. They were just chosen to look good, and yes, they do look quite good.
I don't know if they're scientifically assigned or not. My objection is that there is no information about this image to be found, so it's essentially useless for anything other than admiring pretty colors. Not an image that should be accepted for APOD, IMO.
Chris, how do you assign scientific colors to a narrowband image?
Ann
The choice of mapping is critical to showing certain features. If that choice is carried out with that intent (as opposed to simple aesthetics) I'd very much call that "scientific". The Hubble palette, for instance, was not created for the purpose of making images "pretty". People who design or choose false color and pseudocolor palettes understand human vision, and why specific assignments make sense for specific information goals.
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Ann
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by Ann » Mon Apr 10, 2023 6:22 pm
Chris Peterson wrote: ↑Mon Apr 10, 2023 3:06 pm
Ann wrote: ↑Mon Apr 10, 2023 3:00 pm
Chris Peterson wrote: ↑Mon Apr 10, 2023 1:44 pm
I don't know if they're scientifically assigned or not. My objection is that there is no information about this image to be found, so it's essentially useless for anything other than admiring pretty colors. Not an image that should be accepted for APOD, IMO.
Chris, how do you assign scientific colors to a narrowband image?
Ann
The choice of mapping is critical to showing certain features. If that choice is carried out with that intent (as opposed to simple aesthetics) I'd very much call that "scientific". The Hubble palette, for instance, was not created for the purpose of making images "pretty". People who design or choose false color and pseudocolor palettes understand human vision, and why specific assignments make sense for specific information goals.
I get that. The Hubble palette usually shows OIII as blue, Hα as green and NII (or SII) as red. The wavelengths of Hα and NII (or SII) are both red and so similar that they would look identical in RGB images, but they do represent very different levels of ionization, and the Hubble palette makes them look very clearly different.
I still don't think that the Hubble palette is "scientific", but I can see that it is practical and useful.
Ann
Last edited by Ann on Mon Apr 10, 2023 6:37 pm, edited 1 time in total.
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Chris Peterson
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by Chris Peterson » Mon Apr 10, 2023 6:26 pm
Ann wrote: ↑Mon Apr 10, 2023 6:22 pm
Chris Peterson wrote: ↑Mon Apr 10, 2023 3:06 pm
Ann wrote: ↑Mon Apr 10, 2023 3:00 pm
Chris, how do you assign scientific colors to a narrowband image?
Ann
The choice of mapping is critical to showing certain features. If that choice is carried out with that intent (as opposed to simple aesthetics) I'd very much call that "scientific". The Hubble palette, for instance, was not created for the purpose of making images "pretty". People who design or choose false color and pseudocolor palettes understand human vision, and why specific assignments make sense for specific information goals.
I get that. The Hubble palette usually shows OIII as blue, Hα as green NII (or SII) as red. The wavelengths of Hα and NII (or SII) are both red and so similar that they would look identical in RGB images, but they do represent very different levels of ionization, and the Hubble palette makes them look very clearly different.
I still don't think that the Hubble palette is "scientific", but I can see that it is practical and useful.
Ann
Well, if you have an image, and you apply different palettes to it and choose the one that best shows the information you want to show, I'd call that utilization of the scientific method.
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AVAO
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by AVAO » Mon Apr 10, 2023 8:15 pm
Chris Peterson wrote: ↑Mon Apr 10, 2023 1:44 pm
...Not an image that should be accepted for APOD, IMO.
The author describes it as a SHO image in the original Instagram link.
Unfortunately it happens relatively often that the APOD text don't refers to the original notes of the authors...
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bystander
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by bystander » Mon Apr 10, 2023 8:22 pm
Chris Peterson wrote: ↑Mon Apr 10, 2023 1:44 pm
I don't know if they're scientifically assigned or not. My objection is that there is no information about this image to be found, so it's essentially useless for anything other than admiring pretty colors. Not an image that should be accepted for APOD, IMO.
AVAO wrote: ↑Mon Apr 10, 2023 8:15 pm
The author describes it as a SHO image in the original Instagram link.
Unfortunately it happens relatively often that the APOD text don't refers to the original notes of the authors...
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor
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Chris Peterson
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by Chris Peterson » Mon Apr 10, 2023 10:32 pm
bystander wrote: ↑Mon Apr 10, 2023 8:22 pm
Chris Peterson wrote: ↑Mon Apr 10, 2023 1:44 pm
I don't know if they're scientifically assigned or not. My objection is that there is no information about this image to be found, so it's essentially useless for anything other than admiring pretty colors. Not an image that should be accepted for APOD, IMO.
AVAO wrote: ↑Mon Apr 10, 2023 8:15 pm
The author describes it as a SHO image in the original Instagram link.
Unfortunately it happens relatively often that the APOD text don't refers to the original notes of the authors...
Need a bit more. SHO doesn't define the color mapping, and we aren't informed about exposure time for individual channels or any technical details.
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Ann
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by Ann » Tue Apr 11, 2023 3:48 am
I don't have Instagram, so this is all I get out of it:
looks like a gaseous nebula where star formation takes place. Cataloged as IC 2944, the Running Chicken Nebula spans about 100 light years and lies about 6,000 light years away toward the constellation of the Centaur (Centaurus). The star cluster Collinder 249 is visible embedded in the nebula's glowing gas. Although difficult to discern here, several dark molecular clouds with distinct shapes can be found inside the nebula. These clouds can be more readily seen in the narrower field of view SHO picture. Known as Bok globules, these are dark clouds of dense cosmic dust and gas in which star formation sometimes takes place.
Ann
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