APOD: M31 versus M33 (2013 Sep 26)

Comments and questions about the APOD on the main view screen.
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Beyond
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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Beyond » Fri Sep 27, 2013 1:10 pm

Why would anyone ever want to 'square' a circle :?:
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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Strangerbarry » Fri Sep 27, 2013 1:42 pm

You have to feel sorry for astronomers viewing the universe when the Milky Way merges with M31 and M33. By then the expansion of the universe will have taken all the rest of the galaxies not in our local group out beyond the event horizon where they will be lost to them forever - the universe will appear to be nothing but a central collection of hundreds of billions of stars in an otherwise empty void. With no markers on an inter-galactic scale such as we can see today, material evidence pointing to an expanding universe will be lost, and by extension any inference back in time of a big bang will be impossible. It makes me wonder what information has already receded beyond the event horizon that might have provided important clues to the origin and nature of the universe.

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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Ann » Fri Sep 27, 2013 2:44 pm

My software, Guide, quotes observer Steve Coe when he observed M33.
Steve Coe wrote:
Ultimate Star Party, McDonald Obs, Oct. 95, S=6, T=8, 36", f/5-- M33 in 36" f/5 with 27mm is amazing. The detail that is seen within the arms of this face-on galaxy equals what can be seen in photographs from the 48 inch Schmidt camera, it is un-drawable. The curved arms are filled with bright spots from the core to the tips of the spiral. I counted 20 bright areas in the arm which is see as "up". I can see the difference between Population I and Population II areas in the galaxy. The stars in the core form a smooth surface to the central section that is lightly yellow, whereas the arms are splotchy and bluish.
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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by neufer » Fri Sep 27, 2013 3:22 pm

Beyond wrote:
Why would anyone ever want to 'square' a circle :?:
http://www.tamtwirlers.org/tamination/b1/circle.html
Art Neuendorffer

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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Beyond » Fri Sep 27, 2013 4:43 pm

neufer wrote:
Beyond wrote:
Why would anyone ever want to 'square' a circle :?:
http://www.tamtwirlers.org/tamination/b1/circle.html
'Dancing' around the question, are we :?: :yes: :lol2:
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walker1001

Re: APOD: M31 versus M33 (2013 Sep 26)

Post by walker1001 » Fri Sep 27, 2013 10:15 pm

Thank you Anthony and Chris. Will read linked articles soon.

Jurek

Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Jurek » Sun Feb 09, 2014 5:16 pm

In the lover left of the image there seem to be two identical strings of stars. Possibly some Photoshop stamp tool work?Image

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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by geckzilla » Sun Feb 09, 2014 5:38 pm

Yes, that's some cloned data. You'd have to ask Rogelio why it's there but typically this is done to cover up anomalies like satellite trails or any number of cosmetic defects which are distracting.
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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Jurek Zarzycki » Sun Feb 09, 2014 9:30 pm

geckzilla wrote:Yes, that's some cloned data. You'd have to ask Rogelio why it's there but typically this is done to cover up anomalies like satellite trails or any number of cosmetic defects which are distracting.
Makes me realize that these are not scientific images but rather pretty pictures based on scientific reality. Very pretty indeed.

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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by geckzilla » Sun Feb 09, 2014 9:49 pm

Jurek Zarzycki wrote:
geckzilla wrote:Yes, that's some cloned data. You'd have to ask Rogelio why it's there but typically this is done to cover up anomalies like satellite trails or any number of cosmetic defects which are distracting.
Makes me realize that these are not scientific images but rather pretty pictures based on scientific reality. Very pretty indeed.
Well, the act of removing anomalies themselves is not unscientific. There are scientific ways to exclude them from analysis and then there are quick, hack methods just for the sake of aesthetics. Any given APOD is its own entity and should be treated accordingly. Some are very scientific images and others are there simply for our viewing pleasure. Of course, the act of observation itself is casually scientific, don't you think?
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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Jurek Zarzycki » Mon Feb 10, 2014 4:36 am

geckzilla wrote:
Jurek Zarzycki wrote:
geckzilla wrote:Yes, that's some cloned data. You'd have to ask Rogelio why it's there but typically this is done to cover up anomalies like satellite trails or any number of cosmetic defects which are distracting.
Makes me realize that these are not scientific images but rather pretty pictures based on scientific reality. Very pretty indeed.
Well, the act of removing anomalies themselves is not unscientific. There are scientific ways to exclude them from analysis and then there are quick, hack methods just for the sake of aesthetics. Any given APOD is its own entity and should be treated accordingly. Some are very scientific images and others are there simply for our viewing pleasure. Of course, the act of observation itself is casually scientific, don't you think?
I am not sure what you mean by "the act of observation itself is casually scientific". If you observe something and then document it not in accordance with your observation, and then pass that documentation to others claiming it to be the result of your observation, that's actually a scientific fraud. Or art.
To me the difference between art and science has to do with truth. If you clone stars to your picture where there were no such stars, or a full moon where there was no moon or a shooting star to "liven up your pretty picture" that's art. I can not imagine Edwin Hubble making pinpricks in his plates for "aesthetic reasons". I guess I came to trust APOD for scientific accuracy, so this discovery was a serious disappointment for me. I knew that some of the images were already manipulated as to color saturation and certain burning and dogging but cloning stars where they don't exist is a new low. Now I will have to see these images as only somewhat better than fantasy graphics elsewhere on the web. That is sad, as I hoped to learn science from APOD, and how can one learn science from artists? In other images there are satellite streaks and other cosmetic defects, but at least there are no elements that are pure fiction. In this particular image (M31 versus M33 (2013 Sep 26)) I found other cloned parts. Usually APOD will state "artist's visualization" or "false color", etc. which made me believe that where such statements are not made, I see what was truly recorded. I guess not.

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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Chris Peterson » Mon Feb 10, 2014 5:00 am

Jurek Zarzycki wrote:I am not sure what you mean by "the act of observation itself is casually scientific". If you observe something and then document it not in accordance with your observation, and then pass that documentation to others claiming it to be the result of your observation, that's actually a scientific fraud. Or art.
To me the difference between art and science has to do with truth. If you clone stars to your picture where there were no such stars, or a full moon where there was no moon or a shooting star to "liven up your pretty picture" that's art. I can not imagine Edwin Hubble making pinpricks in his plates for "aesthetic reasons". I guess I came to trust APOD for scientific accuracy, so this discovery was a serious disappointment for me. I knew that some of the images were already manipulated as to color saturation and certain burning and dogging but cloning stars where they don't exist is a new low. Now I will have to see these images as only somewhat better than fantasy graphics elsewhere on the web. That is sad, as I hoped to learn science from APOD, and how can one learn science from artists? In other images there are satellite streaks and other cosmetic defects, but at least there are no elements that are pure fiction. In this particular image (M31 versus M33 (2013 Sep 26)) I found other cloned parts. Usually APOD will state "artist's visualization" or "false color", etc. which made me believe that where such statements are not made, I see what was truly recorded. I guess not.
I don't see why an image can't be both art and science. Consider intent. How does repairing a small area of stars in this image really damage the point, which is to show the relationship between a pair of galaxies, and the material around them? The purpose of this image does not involve the foreground stars, outside of aesthetics.

In fact, every single astronomical image you're likely to encounter, be it on APOD, in a magazine, or in a scientific publication, has been manipulated. Its colors have been balanced and mapped, its intensities reassigned in some nonlinear fashion, its black and white points defined, many instrumental and systematic artifacts removed.
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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Nitpicker » Mon Feb 10, 2014 5:10 am

There can be truth (as much as truth is knowable) in science and art.

But every quality deep sky image is art (many have scientific merit, too). As soon as the light signals are stretched so that the dimmer bits are made brighter, out of natural proportion to the brighter bits, it becomes art. But by manipulating the signals in clever ways, things are revealed that would otherwise remain invisible to us. Furthermore, the visible spectrum of light is only a tiny portion of the full spectrum emitted by the universe. So, if we want to see the full spectrum in an image, we must do unusual things with colours, hence false colour mappings, etc, etc. There is more to "truth" than what we can see with our eyes.

It is possible that the duplication in this APOD was a slight mistake, or it was done to cover a gap in the data, or there was some other reason. But Jurek, I really do think you have overstated your objections, to the point of being ridiculous. There is plenty to learn from APOD and The Starship forum.

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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by geckzilla » Mon Feb 10, 2014 12:39 pm

These things are also removed because they represent a loss of data. I personally avoid cloning if at all possible, instead preferring to drop out small areas, but if there is something really big like a satellite streak it's almost impossible to get rid of discreetly. You could fill the entire APOD description with minute details of all of the things that went on in the processing and then push the interesting science off the end of the page. You know what else happens anytime something completely normal like a satellite streak or some cosmic rays appear? People get confused. Really confused. They start saying that these must be aliens or all of these artifacts must be galaxies, etc. It's worthwhile to reduce the confusion so that things get quickly to the point and people are not overloaded with inane and boring details. You can get angry about it all you want but it's still a very good way to handle things.
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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by NGC3314 » Mon Feb 10, 2014 5:01 pm

Indeed. Experience has shown (tracked by, for example, the HST outreach staff) that artifacts such as cosmic rays, bleeding trails from saturated stars, and satellite trails can be enormously distracting for the impact of images on a broad public. Research articles are full of images marred by such things, and rather quickly astronomers barely even notice them, but they take explanation. There's a discussion in this article: What Determines the Aesthetic Appeal of Astronomical Images?, written by three people active in the ESA Hubble outreach.
Experience shows that one of the things that disturbs the viewing pleasure for members of the public is residual artefacts from
the sensor or the telescope. The rule of thumb is simple: while scientists may be able to concentrate only on the parts of the data that are relevant to them, ignoring artefacts, members of the public will focus on anything of non-cosmic (origin). All artefacts must be removed in order to not distract the eye, disturb the aesthetic appeal, or to waste the audience’s finite attention span on aspects of the image that are not part of the scientific outreach message. This is something that ESO and ESA/Hubble expend significant manpower on, often to the order of one or two hundred hours of manual cleaning work for a large image. The number of frames must be sufficient to filter cosmic rays and detector blemishes and to cover inter-chip gaps during astronomical processing.
How well this processing can be done in particular cases with different constraints is a more complex question...

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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Chris Peterson » Mon Feb 10, 2014 5:10 pm

NGC3314 wrote:Indeed. Experience has shown (tracked by, for example, the HST outreach staff) that artifacts such as cosmic rays, bleeding trails from saturated stars, and satellite trails can be enormously distracting for the impact of images on a broad public. Research articles are full of images marred by such things, and rather quickly astronomers barely even notice them, but they take explanation.
Even research articles rarely use raw images for evidence. They are almost always processed- contrast stretched, color mapped, calibrated to remove some artifacts. The processing isn't for aesthetics, as a rule (although aesthetics can quite reasonably be a factor), but the processing is still there.
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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by geckzilla » Mon Feb 10, 2014 6:16 pm

NGC3314 wrote:There's a discussion in this article: What Determines the Aesthetic Appeal of Astronomical Images?, written by three people active in the ESA Hubble outreach.
Oh, I hadn't seen that yet. Thanks for sharing the link. That's a great article. Previously I managed to find myself at this website which has some very useful articles dealing with aesthetics, especially with the invisible light. They also have an article in CAP issue #10.
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Re: APOD: M31 versus M33 (2013 Sep 26)

Post by Anthony Barreiro » Mon Feb 10, 2014 6:52 pm

This has been an interesting discussion, and seems to touch on the broader question of epistemology, the study of knowledge and justified belief.

Every perception of the outside world is mediated in some way. Even if we're standing outside looking at the stars on a clear night, not using a telescope or taking pictures, the relationship between how the sky looks and how things "really are" is complicated. The stars that are closer look brighter even though their absolute brightness may be much less than the faint distant stars. The stars are twinkling because their light is passing through Earth's atmosphere. Our nervous systems are tuned to enhance the contrast between the bright stars and the darkness of the sky. Etc. Every time we believe something or know that something is true we're making some very sophisticated decisions, consciously or unconsciously, about the coherence of our own perceptions and thoughts, standards of evidence, reliability, etc., always in the context of some ambiguity and uncertainty.

So when we look at an astronomical image, it seems not just unrealistic but also unhelpful to make a binary decision about whether this image is "true" (or "scientific") vs. "false" (or "artistic"). Rather if we want to increase our understanding of the phenomenon being pictured, it helps to know how the image was processed, what information may have been lost in processing (e.g. the presence of satellite trails, cosmic ray flashes, or diffraction spikes from stars cropped out of the image), and what information is being highlighted. Based on our understanding of the phenomenon being portrayed, our previous experience of other images of similar objects, and our aesthetic sensibilities, we may make judgments about the pedagogical value and visual appeal of the image. But a sound judgment will be based on an appreciation of the inevitable trade-offs involved in creating an image, not on the assumption that there is one absolute, objective, ideal best image against which all other possible images are compared.
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