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What is background and what isn't?

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#1 deSitter

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Posted 03 November 2013 - 07:15 AM

Here's an excellent article that realizes the Internet's potential to communicate science.

http://cosmologyscie...lution-surpr...

-drl

#2 Charlie B

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Posted 03 November 2013 - 08:26 AM

Here is an interesting article about Planck, which was not launched in the time frame of Dilworth's article.

Charlie B

#3 Charlie B

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Posted 03 November 2013 - 08:44 AM

Here's an excellent article that realizes the Internet's potential to communicate science.



Dilworth makes it appear that COBE's 2 pixels were because of cheap design. He also makes a lot of comparisons to mega-pixel cameras. However, COBE was designed as a non-imaging instrument to measure differential radiation near 4 degrees kelvin. Most hot sources in the microwave region have Planck curves with much different slopes in the microwave region.

He does have a point about it's low resolution, which is why we have WMAP and Planck instruments, but I think that the whole tone of the article is misleading. It would be better balanced to explain the nature of Planck curves and what is expected in the microwave region with different foreground sources, from stars, galaxies, etc.

Regards,

Charlie B

#4 GregLee1

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Posted 03 November 2013 - 12:33 PM

Here's an excellent article that realizes the Internet's potential to communicate science.

http://cosmologyscie...lution-surpr...

He writes:

However, by contrast, we do not have anything near the same certainty that there is any background microwave radiation because you just can’t take a picture of it, you have to calculate it.



Surely no one with any notion of how a digital camera works could say such a thing. If it's calculated, it's not a picture??

#5 Charlie B

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Posted 03 November 2013 - 01:31 PM

George Smoot's website is here. You might like his lecture "Design of the Universe".

Charlie B

#6 deSitter

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Posted 03 November 2013 - 10:34 PM

Extremely over-processed image - look, I have small scale fluctuations on
my wall - except they are pure artifact:


FUNNY

-drl

#7 GregLee1

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Posted 03 November 2013 - 10:46 PM

Surely no one with any notion of how a digital camera works could say such a thing. If it's calculated, it's not a picture??


Surely no one with any notion of how image processing works could say such a
thing. Just what do you think software like Photoshop does when you adjust an
image?


Photoshop is not a digital camera, so what does this have to do with what I said? What do you think a digital camera does when you don't adjust an image? Do you think there is no image processing going on?

Photography, these days, always involves image processing. You don't see some sort of direct rendition of individual CCD cell responses. If you want to judge whether this processing results in a more versus less faithful rendering, you'd have consider the intent and the specific sort of processing.

#8 deSitter

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Posted 03 November 2013 - 10:55 PM

Here's an excellent article that realizes the Internet's potential to communicate science.



Dilworth makes it appear that COBE's 2 pixels were because of cheap design. He also makes a lot of comparisons to mega-pixel cameras. However, COBE was designed as a non-imaging instrument to measure differential radiation near 4 degrees kelvin. Most hot sources in the microwave region have Planck curves with much different slopes in the microwave region.

He does have a point about it's low resolution, which is why we have WMAP and Planck instruments, but I think that the whole tone of the article is misleading. It would be better balanced to explain the nature of Planck curves and what is expected in the microwave region with different foreground sources, from stars, galaxies, etc.

Regards,

Charlie B


I think the point he is trying make, is that the mass of galaxies found in deep fields contributes to foreground in a way that is easy to overlook and impossible to settle without high resolution. Michael Disney relates a story of how the designers of the HST sensors were told by cosmologists to not worry about the background galaxies, because there would not BE any to worry about!

-drl

#9 PeterR280

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Posted 03 November 2013 - 11:01 PM

It's much easier to see that's it's a Celestron 80ED in the unprocessed image.

#10 Mister T

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Posted 04 November 2013 - 07:55 AM

The CMBR is really an effect from LEAD PAINT!!

get your house and your universe tested!! :help:

#11 llanitedave

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Posted 04 November 2013 - 11:08 AM

When you get right down to it, the system of eye and brain that provides vision does a whole heck of a lot of image processing too.

#12 Charlie B

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Posted 04 November 2013 - 12:26 PM

I think the point he is trying make, is that the mass of galaxies found in deep fields contributes to foreground in a way that is easy to overlook and impossible to settle without high resolution.



I understood his point, but his examples are not really very good.
1. The DMR (Differential Microwave Radiometer) is not a camera and does not have pixels. It is merely measuring the difference in temperature at 2 areas of the sky and with lots of revisits over the 4 year lifetime. At the frequencies used, the CBR is about 1000 times greater than the background radiation.

2. He said "(“Angular Resolution” simply means how much detail is in an image. A camera with more megapixels has a greater angular resolution; more is better.)". This is true, but meaningless when talking about the DMR. Sensitivity is the key issue for COBE, secondary is angular resolution. It's mission was to look for ansiotropic radiation in the background

3. There were two other instruments DIRBE and FIRAS on COBE see here that he does not mention. DIRBE's (Diffuse Infrared Background Experiment) primary mission was to map the IR sky to develop foreground information at wavelengths that would include dust radiation.

Overall, I think his analogs were completely off the mark, but the higer resolution of WMAP and PLANCK did improve CBR results. However, when looking a universe-sized scales, you don't want too much resolution.

Regards,

Charlie B


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