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Compare Webb's Images to Hubble

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Re: Compare Webb's Images to Hubble

#41

Post by agrajag »

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…

For the wavelengths that the telescopes are designed to observe (primarily ultraviolet & visible for Hubble, though it can do a little bit of infrared, while JWST looks at Infra-red and mid-infrared) resolution is fairly comparable, though JWST has a much wider field of view and doesn't half to sit idle when it orbits the sun side of the earth like Hubble does.

A major issue with Hubble & JWST comparisons is just that they're designed to look at different wavelengths of light. A lot of what JWST will see is completely invisible to Hubble, and no amount of observing time can compensate for that.

Re: Compare Webb's Images to Hubble

#44

Post by weaksauce »

protoster wrote: post #28

Bug report: On Firefox the difference wiper thing doesn't appear for the last image (Carina Nebula), it only shows the full Webb image.

funny enough that one didn't work on chrome but worked in firefox nightly albeit a distorted version that only showed the top left corner of it... I'm not sure hubble shot the full version?

https://i.imgur.com/oBK3sWE.png

Re: Compare Webb's Images to Hubble

#47

Post by mtlmtlmtlmtl »

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…

IANA{astrophysicist, space engineer} but I do follow this closely and have what I call a working armchair understanding of this stuff. Anyone from relevant fields is welcome to gently correct any imprecisions. I always want to learn more and will thank you for it

>could Hubble achieve the same quality of images as Webb if it was given 100x (or whatever) more time exposure?

No, for a different and simpler reason: Hubble isn't as sensitive in the infrared as Webb. A lot of the stars and structure Webb has revealed in the two nebulae especially is due to it picking up a lot more of the infrared light to which the gas and dust of the nebulae are essentially transparent. In other words the data is qualitatively different in addition to the increased resolution. This also will see much older light which is redshifted(the longer the travel, the greater the shift) out of Hubble's range of sensitivity.

As for the quantitative part, I guess mirror size is what you'd want to look at? Hubble has a single circular primary mirror with a diameter of 2.4 metres.[0]

Webb has 18 hexagonal mirror segments that are combined into the equivalent of a circular mirror with diameter 6.5m. That is ~6.25 times the light collection area of Hubble(25.4m² vs 4m²)[1]

0: https://en.wikipedia.org/wiki/Hubble_Space_Telescope

1: https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Fea...

Re: Compare Webb's Images to Hubble

#48

Post by mtlmtlmtlmtl »

pythonguython wrote: post #33
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.

This is true, but he was asking specifically about a metric that's independent of the exposure time.

Re: Compare Webb's Images to Hubble

#49

Post by IshKebab »

red_trumpet wrote: post #32
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.

Motion of what?

Re: Compare Webb's Images to Hubble

#50

Post by JacobThreeThree »

kadoban wrote: post #9
mholt wrote: post #4

Here's a backyard telescope versus Webb: https://twitter.com/AJamesMcCarthy/status/154694183270093209... More comparisons on Twitter, some zoomed in: - https://twitter.com/Batsuto_/status/1546899241880240128 - https://twitter.com/Batsuto_/status/1546900387931766784 - https://twitter.com/JBWillcox/status/1546881033597075457 - https://twitter.com/jason4short/status/1546626672488632321 I'm not a physicist, so I've only…

They're not lens flares, but they're still an artifact of the system, which is probably what most people mean by "lens flare" anyway, due to lack of a better common term.

According to the Wikipedia definition, I'd say that Webb's artifacts could be classified as "lens flares".

>This happens through light scattered by the imaging mechanism itself, for example through internal reflection and forward scatter from material imperfections in the lens. Lenses with large numbers of elements such as zooms tend to have more lens flare, as they contain a relatively large number of interfaces at which internal scattering may occur.

https://en.wikipedia.org/wiki/Lens_flare

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