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Not exactly macro, but what technique!
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Lou Jost



Joined: 04 Sep 2015
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PostPosted: Wed Apr 10, 2019 9:45 am    Post subject: Not exactly macro, but what technique! Reply with quote

We've sometimes wondered about whether our images show false detail. Scientists also wonder about this in their images. Here is the most amazing effort ever undertaken to construct the truest possible image from noisy sensor data:

https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85

The subject is the size of the whole solar system!!!!!

Also the biggest camera ever made (size of the whole earth) , and the most expensive.
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Chris S.
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PostPosted: Wed Apr 10, 2019 11:20 pm    Post subject: Reply with quote

Lou, thanks for the link to the scientific letter describing this image and the research behind it. It's not easy to slog through, but is fascinating.

Here are a couple of well-written, easier-to-read articles by science-reporters with useful perspective:

I do think that viewers of this image should be aware that it is a visual representation of data acquired in a different region of the electromagnetic spectrum from visible light--a region near the border between radio and microwave frequencies. And that these data have been crunched through a number of protocols that may twist them into something they are not. Confirmation bias--human beings unconsciously nudging noisy data into what they expect to see--is an all-too-real phenomenon.

This said, the measures these scientists took to reduce the chances of confirmation bias verge on Herculean. Whether their conclusions prove right or wrong in the end, kudos for their discipline.

One thing this work has in common with ours is the tiny field of view. The image of the putative black hole has a field of view similar to a picture of an orange sitting on the moon, viewed from Earth. Wow!

--Chris S.


Last edited by Chris S. on Thu Apr 11, 2019 12:54 am; edited 1 time in total
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Perl



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PostPosted: Thu Apr 11, 2019 12:54 am    Post subject: Reply with quote

Strange that they present this non Visual data as a Picture
not correct in a science view

Should be named data model visualisation or something !

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Pär
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Chris S.
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PostPosted: Thu Apr 11, 2019 1:07 am    Post subject: Reply with quote

Perl wrote:
Strange that they present this non Visual data as a Picture, not correct in a science view

Should be named data model visualisation or something!

Pär, aren't you and I saying much the same thing in different words, and in close agreement?

--Chris S.
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Perl



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PostPosted: Thu Apr 11, 2019 1:13 am    Post subject: Reply with quote

Yes Chris !
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pär
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Lou Jost



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PostPosted: Thu Apr 11, 2019 5:25 am    Post subject: Reply with quote

It is not that different from UV or IR photography; the electromagnetic spectrum is a lot bigger than our piddly rods and cones can detect.

I like the way they had four different teams work on the image processing in complete isolation from each other, and also how they tried synthetic data. They worked hard to avoid confirmation bias, and the consensus seems to be that they were successful.

And yes, the angular resolution is incredible!
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mawyatt



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PostPosted: Thu Apr 11, 2019 7:46 am    Post subject: Reply with quote

Lou,

This is really amazing.

The electronics folks call this Synthetic Aperture, the concepts originated long ago with radar. The part that prevented this level of separation until now is the synchronizing of the receivers (telescopes).

Optically I believe this has been done at Mauna Kea, but these receivers (telescopes) are not far apart, thus the optical synchronizing is possible.

These techniques should open up all sorts on new possibilities.

BTW folks are building chips that use these same principles, it's called beam forming or phased arrays, you will see this in the later versions 5G phones. We published an Invited Paper in the IEEE Spectrum in Sept 2005, "Smart Phased Array SoCs: A Novel Application for Advanced SiGe HBT BiCMOS Technology", this work originated back in 2000 with a USG customer. Very Happy


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Lou Jost



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PostPosted: Thu Apr 11, 2019 7:55 am    Post subject: Reply with quote

Mike, that's a very interesting connection!
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iconoclastica



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PostPosted: Thu Apr 11, 2019 2:14 pm    Post subject: Reply with quote

Chris S. wrote:
I do think that viewers of this image should be aware that it is a visual representation of data acquired in a different region of the electromagnetic spectrum from visible light--a region near the border between radio and microwave frequencies. And that these data have been crunched through a number of protocols that may twist them into something they are not.

So, not unlike the processing of a digital camera with its optical trickery, electronic components and a sequence of software. Especially when the subject is microscopic so not an image, but an interference pattern. The wavelength is different from visual light, but I never heard that people have interpretation problems with IR images (heat photography), the UV vision of insects, or even electron microscopy imagery. Though you could call it a heat map representation, I suppose.
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rjlittlefield
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PostPosted: Fri Apr 12, 2019 12:00 pm    Post subject: Reply with quote

Another good article: "That image of a black hole you saw everywhere? Thank this grad student for making it possible."

--Rik
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Chris S.
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PostPosted: Sat Apr 13, 2019 10:37 pm    Post subject: Reply with quote

About two years ago (Apr 28, 2017), Katie Bouman, the grad student in the article Rik referenced above, did a TED Talk that's worth watching. She discussed the work then in progress, how the team was conducting it, what they expected to see, and methods they were working on to reduce the chance of bias.

A thing that's clear from the talk is that the research team's pre-experiment expectations, and the image that eventually resulted from the experiment, match closely. Take a look at the talk's "simulated black hole images." That the eventual image ended up closely matching the researchers' expectations may be the result of exemplary theorizing; but we have to leave room for the possibility that expectations inadvertently guided the data analysis toward hoped-for goals. While there were four teams independently interpreting the data, every team was apparently seeded with a strongly-held common vision of what a black hole image should look like.

The image is very cool, and I hope it turns out to be revelatory. But because I hope that, I should be extra skeptical. As this image surely fulfills the hopes and dreams of the researchers who produced it, a high degree of skepticism is their intellectual duty. They surely sense this duty very strongly.

It's notable that the team published its results as a letter rather than an article. In academic publishing, a letter commonly indicates either a minor finding or an important work in progress. As this image is epoch-making, "minor finding" is out of the question. And the research seems as complete as the team can make it, cross-checked in every way they can think of. My guess is that publishing as a letter is an invitation for others in their field: "Attack, defend, review, discuss." While this standard for any scientific finding, the nuance here may be to particularly welcome it.

--Chris S.
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Lou Jost



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PostPosted: Sun Apr 14, 2019 3:51 am    Post subject: Reply with quote

Chris, in some fields anyway, "Letters" are also faster to publish, and that might have been a factor in choosing the format. But yes, they have been very explicit about their process, deliberately so, in order that people can criticize and test. Good science in every way.
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mawyatt



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PostPosted: Sun Apr 14, 2019 5:09 am    Post subject: Reply with quote

Its shame that Stephen Hawking couldn't have seen this before his death. This is certainly opening up a new technique for space exploration.

I can envision expanding this Synthentic Aperture Beam Forming Radio Telescope technique into space with geosynchronous (or beyond) satellites, which will have an effective diameter of 72Km!! The technology is here today with small atomic clocks for synchronizing, and the small satellites which would "open up" a much larger physical antenna once deployed.

Interesting times indeed!!

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Lou Jost



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PostPosted: Sun Apr 14, 2019 6:11 pm    Post subject: Reply with quote

Mike, during the question-and-answer session following the announcement, one of the scientists said that this would indeed be the next step, to get a bigger baseline and also to escape weather problems. The weather problems are huge with an earth-based array because you need good weather simultaneously all over the world.
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mawyatt



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PostPosted: Mon Apr 15, 2019 4:51 am    Post subject: Reply with quote

Lou, that makes sense!! 1st thought that I got after reading this was they'll want a bigger aperture for better resolution, and space is the solution!

Since atomic clocks are not very good good for short term stability I understand, you might be able to just launch one small sat with the clock and the other small sats could synch up via a microwave link. Each sat would have a quartz crystal for short term stability, that is synched up with the atomic clock with long integration periods.

Sounds like a fun project for the lucky folks that get to do it!!

Best,
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