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Compare Webb's Images to Hubble

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Re: Compare Webb's Images to Hubble

#31

Post by dylan604 »

dynm wrote: post #26

Question for anyone who happens to be an expert: Is there any way to quantify how much better Webb is independently of the amount of time used to take the exposures? Like, could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure? I'm trying to understand how much the improvement is "speed of convergence" vs. "quality of asymptotic result". (Though... is that even a…

No, expsoure time is not enough. Resolution is a factor of the size of the primary mirror. Exposure time just allows capture of photons at that resolution. With the JWST primary mirror dwarfing the Hubble's, then it will always have better imagery.

Re: Compare Webb's Images to Hubble

#32

Post by red_trumpet »

dynm wrote: post #26

Question for anyone who happens to be an expert: Is there any way to quantify how much better Webb is independently of the amount of time used to take the exposures? Like, could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure? I'm trying to understand how much the improvement is "speed of convergence" vs. "quality of asymptotic result". (Though... is that even a…

I'm no expert either, but I imagine that high exposure times come with more motion blur. So just cranking up exposure time does not necessarily result in better pictures.

Re: Compare Webb's Images to Hubble

#33

Post by pythonguython »

dynm wrote: post #26

Question for anyone who happens to be an expert: Is there any way to quantify how much better Webb is independently of the amount of time used to take the exposures? Like, could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure? I'm trying to understand how much the improvement is "speed of convergence" vs. "quality of asymptotic result". (Though... is that even a…

Not an expert, but one metric to demonstrate Webb’s capability is that Hubble’s deep field exposure took 10 days, and Webb did it in 12.5 hours.

Re: Compare Webb's Images to Hubble

#34

Post by CitizenKane »

bandyaboot wrote: post #29

I’m curious what’s going on in the upper left area of the Carina Nebula image. The dust can’t have actually cleared out that much since the Hubble shot was taken, could it?

I believe the Hubble shot is more in the visible spectrum whereas the JWST images are in infrared so there are structures in each shot that don't necessarily show up in the analogous image.

Re: Compare Webb's Images to Hubble

#35

Post by treesknees »

bandyaboot wrote: post #29

I’m curious what’s going on in the upper left area of the Carina Nebula image. The dust can’t have actually cleared out that much since the Hubble shot was taken, could it?

I'm not an expert, but from what I came across online earlier, the Hubble telescope sees more of the visible/UV spectrum than the Webb telescope. So it may just be a difference in what's captured.

This site has a diagram of the spectrum that shows which portions are covered by each telescope, as well as some video clips comparing photos captured by Hubble and Webb. The first video of the Lagoon Nebula (M8) demonstrates what I'm saying pretty well.

https://webbtelescope.org/webb-science/the-observatory/infra...

Re: Compare Webb's Images to Hubble

#36

Post by unethical_ban »

dynm wrote: post #26

Question for anyone who happens to be an expert: Is there any way to quantify how much better Webb is independently of the amount of time used to take the exposures? Like, could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure? I'm trying to understand how much the improvement is "speed of convergence" vs. "quality of asymptotic result". (Though... is that even a…

Webb's physical dimensions are larger than Hubble's. The "collecting area" of Web is 273 sq ft to Hubble's 46, per Wikipedia. The two telescopes are sensitive to different (but somewhat overlapping) bands of light. Hubble worked through the visible spectrum while JWST is almost exclusively infrared.

To the "can Hubble do anything Webb can do but with more time", the answer is no, due to the lack of mid-infrared sensitivity, among other things like atmosphere.

Re: Compare Webb's Images to Hubble

#38

Post by Osmium »

dynm wrote: post #26

Question for anyone who happens to be an expert: Is there any way to quantify how much better Webb is independently of the amount of time used to take the exposures? Like, could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure? I'm trying to understand how much the improvement is "speed of convergence" vs. "quality of asymptotic result". (Though... is that even a…

Regardless of exposure, you have to consider wavelength. There are some things JWST can see that are completely invisible to Hubble, or, similarly, there are objects that are opaque to Hubble that JWST can see right through. Just look at all the extra stars that appear in the image of the Carina Nebula for an example of that.

Re: Compare Webb's Images to Hubble

#39

Post by 0xfaded »

dylan604 wrote: post #31
dynm wrote: post #26

Question for anyone who happens to be an expert: Is there any way to quantify how much better Webb is independently of the amount of time used to take the exposures? Like, could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure? I'm trying to understand how much the improvement is "speed of convergence" vs. "quality of asymptotic result". (Though... is that even a…

No, expsoure time is not enough. Resolution is a factor of the size of the primary mirror. Exposure time just allows capture of photons at that resolution. With the JWST primary mirror dwarfing the Hubble's, then it will always have better imagery.

Wavelength is also a factor. Huygens optics has a great video on this. tldr; angular resolution is about the same as the Hubble.

https://youtu.be/gOpbXBppUEU

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