[HN Gopher] Compare Webb's Images to Hubble ___________________________________________________________________ Compare Webb's Images to Hubble Author : hexomancer Score : 558 points Date : 2022-07-12 18:41 UTC (4 hours ago) (HTM) web link (johnedchristensen.github.io) (TXT) w3m dump (johnedchristensen.github.io) | ijidak wrote: | This is perfect! Without this context it's hard to appreciate how | much better Webb is! | boomskats wrote: | The sliders break when page zoom is anything other than 100% :/ | mholt wrote: | 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 recently learned about | redshift. Hubble's deep field images were very dark red/orange | because further objects appear redder (into infrared) before they | disappear to the observer. Webb's sensors are more red/infrared- | sensitive than Hubble's, so along with extremely fine, super- | cooled optics using exotic materials to align and capture every | single photon, its red sensitivity allows Webb to peer deeper, | further, and dimmer than we've ever been able to before. | | And I've read that the "spikes" coming off the brighter stars are | generally from stars in our own galaxy and they're not lens | flares. They're caused by the edges of the telescope. Hubble's | stars would have 4 spikes in a cross; Webb has 6 in a snowflake | because of the shape of Webb's mirrors having 6 sides. Or | something like that. | dr_orpheus wrote: | The spikes are caused by diffraction of light around the struts | supporting the secondary mirror. Hubble has 4 supports for the | secondary mirror. JWST has 3 support for the secondary mirror, | which because...physics (I don't know I'm not an optics | guy)...manifests as 6 diffraction lines. | | https://en.wikipedia.org/wiki/Diffraction_spike | | EDIT: It may be caused by both the diffraction spikes from the | supports struts and the shape of the mirror and aperture. I'm | not really sure. The JWST images also seem to have two | additional small spikes that look more like the diffraction | pattern from a single strut, which could also be a support | strut for a stop further down the optics chain. | WorldMaker wrote: | Apparently the Diffraction spikes come from both the primary | mirror shapes and the struts holding the secondary mirror. | The primary mirrors of the JWST are hexagonal which would | explain hexagonal looking effects. The three struts are | apparently designed so that two of the struts match the | hexagonal mirror angles at all times and are "hidden" inside. | (The third strut apparently sometimes causes two much smaller | "horizon" spikes for very, very bright objects.) | | Hank Green on TikTok did a neat, quick demonstration in video | form. | dr_orpheus wrote: | Oh, thank you that makes sense. And due to the folding of | the mirror and launch envelope constraints they can't | equally space the three struts such that ALL are inside the | diffraction of the hexagonal mirror. | mintyLemon wrote: | Link to that Hank Green video on YouTube: | https://m.youtube.com/watch?v=Y7ieVkK-Cz0 | kadoban wrote: | 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. | JacobThreeThree wrote: | 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 | foxhop wrote: | thank you very informative. | [deleted] | thatswrong0 wrote: | Just needs to include exposure time differences and this is | perfect. Glad to witness the power of this fully armed and | operational battle station. | laserbeam wrote: | It's my understanding that Webb used much shorter exposure | times than Hubble, correct? | tambourine_man wrote: | Yes, hours vs days, which makes them a lot more impressive if | you know a bit about photography. | | I wanna see what this thing is able to do with a 10 days | exposure. Let it loose. | dylan604 wrote: | >I wanna see what this thing is able to do with a 10 days | exposure. | | Ever seen a solid white square? =) | | As with all things, it totally depends on what's being | imaged. Exposing the Orion Nebula for 10 days would result | in a totally over exposed image looking like a solid white | square. | nooyurrsdey wrote: | This is a wonderful way to visualize side by side images like | this. | | Great work, it feels smooth and intuitive. | hparadiz wrote: | I'm actually most looking forward to seeing a picture of our | planets. I wonder what kind of resolution we'll get of Jupiter | and Mars in particular. | | Also curious about what the closest stars to our solar system | would look like. Of course it also makes me wonder what would we | be able to see given a 100x increase in aperture. Like for | example if we could send up something extremely large on | Starship. Would we be able to image planets in our local group? | Exciting! | mtlmtlmtlmtl wrote: | I love this. But the Carina Nebula doesn't work on Firefox for | Android. It just displays the JWST image. | yellowapple wrote: | For me it shows the top half of the Hubble version, but not the | bottom. | wlesieutre wrote: | That's the extent of the Hubble original | | https://hubblesite.org/contents/media/images/2008/34/2405-Im. | .. | mtlmtlmtlmtl wrote: | That makes sense then. I have two suggestions if the person | who made this is reading: maybe fill out the hubble image | with black so it can line up with the JWST image, might | make the interface less janky? Or if someone knows of a | larger imagine from another telescope(Spitzer?) That could | be a more interesting comparison for that particular | observation. | red_trumpet wrote: | Changing the orientation of my phone from portrait to landscape | while on the site somewhat solved this. | protoster wrote: | Bug report: On Firefox the difference wiper thing doesn't appear | for the last image (Carina Nebula), it only shows the full Webb | image. | weaksauce wrote: | 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 | nathancahill wrote: | Working on latest FF on Mac. The Hubble image is just smaller. | bandyaboot wrote: | 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? | dylan604 wrote: | Lots of visible light is reflected in the Hubble image from the | dust causing it to look like it does. As others have said, the | JWST does not suffer from that as it "sees" past those | frequencies revealing new details instead. | CitizenKane wrote: | 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. | treesknees wrote: | 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... | pkaye wrote: | With infrared you can see through the dust. | xenadu02 wrote: | Indeed - that's one of the primary reasons to build the JWT: | Dust and gas blocks our view in various cases so we want to | take images in wavelengths that are more transparent to that | debris. | wanderingstan wrote: | Amazing! Would be interesting to also compare with earth-bound | telescopes, to really appreciate the progress. | prohobo wrote: | Is it absurd to think that maybe the Carina Nebula's shape has | visibly shifted a bit since the last photo? | baltimore wrote: | Now build a zoomable full-res version. Because I am spoiled and | want the internet to do things for me. | yread wrote: | ESA got your back: | | quintet: https://esawebb.org/images/weic2208a/zoomable/ | | https://esawebb.org/images/weic2208b/zoomable/ | | carina: https://esawebb.org/images/weic2205a/zoomable/ | | https://esawebb.org/images/weic2205b/zoomable/ | | Southern ring https://esawebb.org/images/weic2207a/zoomable/ | | https://esawebb.org/images/weic2207b/zoomable/ | | https://esawebb.org/images/weic2207c/zoomable/ | | Deep field https://esawebb.org/images/weic2209a/zoomable/ | | https://esawebb.org/images/weic2209b/zoomable/ | mrleinad wrote: | Well, I found my next set of ultrawide wallpapers for my 49" | monitor :) Thanks! | mtlmtlmtlmtl wrote: | Not a UI or web guy scaling the slider with zoom might do the | trick? | angryGhost wrote: | born too early... | echelon wrote: | For the machines that will replace us. | bastardoperator wrote: | Downvote me to hell, but as a person who has zero understanding | of what differentiates Hubble from Webb, the pictures alone just | aren't doing it for me. I was excited to see something completely | new given 30 years and 10 billion dollars and instead I feel like | I'm seeing what looks like an enterprise upgrade and feel | slightly disappointed. | | What am I missing? | Mangalor wrote: | These are just the first few images. Give it time. | stevage wrote: | With respect, the goal of a major scientific project is not to | impress the layperson with pretty pictures. | fleddr wrote: | Pretty expensive Insta filter. | _benj wrote: | just WOW! I always feel so tiny when considering the absurd | dimensions of space brought shockingly vivid with this images! | supernova87a wrote: | For the professional (or former professional) astronomers among | us, I will make my somewhat amused observation that what people | are most paying attention to is not really the distinguishing | features of JWST. | | People seem most impressed by the apparent increase in resolution | of the images, which is not from a certain point of view the | hardest thing to do . HST might have done that if its instruments | had been of different pixel size or imaging array size / focal | length. Ok, the much larger mirror _is_ an achievement. But | anyway, the resolution of the images is often not what really is | the limiting factor for photometric observations. Yes it is | sharper /higher resolution, but that wasn't the key selling | point. | | The new thing is observations in the IR, which is somewhat a | technical footnote in many gushing announcements of these images | (or some discussion here too). And the general public knows | little about that detail's importance, especially since the | images are stylized / colored anyway to look just like RGB images | that we are so familiar with. But everyone can easily appreciate | a sharper image. | | Anyway, still a momentous achievement. And thank god we have a | scientific field where stunning images was enough to get the | public to support a $10B project. | | ** | | Edit to add: I did not mean to detract from or diminish anyone's | appreciation of the images and accomplishment at whatever level | they are enjoyed. And of course many here are technically | knowledgeable about the IR aspect. I just write to point out that | for the most headline-grabbing images and newspaper writers, the | sharpness of the images over the actual IR frontier is what grabs | the attention. | tigershark wrote: | The increased resolution is extremely important given that the | diffraction threshold is function of the wavelength and the | mirror diameter. And you can clearly see that in the MIRI | images at a longer wavelength that have a noticeably lower | resolution compared to Nircam. If Webb mirror was as big as | Hubble the resolution would have been bad in the long | wavelengths. Hubble couldn't have had a better resolution with | better instruments, he was already limited by its aberration | problem and the new instruments were designed to mitigate that | problem. | nacogo wrote: | Agreed! In the SMACS 0723 image, there is a red spiral galaxy | near the top right which is effectively not present in the HST | image because it was redshifted out of the spectrum. This | implies it's one of the galaxies receding the fastest from us | in the image right? And therefore also among the oldest and | farthest away? | | https://blog.wolfd.me/hubble-jwst/ | lisper wrote: | Yes, exactly right. (AFAIK, IANAA) | t3estabc wrote: | how about now/ I am trying to get this to work and I am | getting an error. That's fine I guess. I am just trying to | get it to work. I am going to have to leave | supernova87a wrote: | Yes, well 2 possible effects: | | 1) as you said, its flux is predominantly in the IR | | 2) it could have been fainter than the sensitivity of the HST | instruments but now seen because of the sensitivity of JWST | | But given that it appears so bright in the JWST image similar | to other nearby galaxies that _do_ appear in the HST image, | your bet on #1 seems reasonable. | | Also there is another point: rather than a highly redshifted | galaxy it could be a very dusty nearby galaxy (also appearing | very red) but if I remember right, that would have a slightly | different signature. Dusty galaxies often aren't entirely | dusty and have "lanes/channels/streaks" of dust that are | interspersed among normal stellar regions, so if it were | that, you would be seeing some bright spots outside the | infrared. But this one has the shape of a normal galaxy but | red all over, suggesting something affects the whole galaxy | -- i.e. redshift. | libraryatnight wrote: | This is so dismissive and insulting. Slack channels at work are | all abuzz about this today. Many of the boards and communities | I visit are too, and while yes there's definite wowing on the | resolution - all of them are talking about the IR. Trying to | understand what it means and learn. Support reps through | engineers at work asking questions, sending links. Even in the | comments of reddit of all places people are curious. This is | genuinely cool and people are engaging with it and you're | dismissive of the public, the scientists, and just about | everything in between. | | I'm sure you were well intentioned, but this comment read all | kinds of rude and negative. | Enginerrrd wrote: | I think this is a little harsh, but I actually generally | agree. I'm a total laymen here and my PRIMARY TAKEAWAY has | been the IR component and how much more and further away you | can see because of it. | mtlmtlmtlmtl wrote: | Right. After the initial "wow factor" has settled down, what's | been most striking to me is the level of detail that's no | longer obscured by gas and dust in these nebulae due to MIRI. I | know very little about the study of stellar nurseries or | planetary nebulae but I've seen enough pre-JWST images of them | to know that astrophysicists just got a whole lot to sink their | teeth into and I look forward to seeing further developments as | more data is collected and existing data is studied. | [deleted] | matesz wrote: | Did anybody make a comparison for rough estimation on the number | of galaxies in the observable universe based on hubble vs webb? | woevdbz wrote: | It's striking how much more flamelike the structures appear to | be, with the added resolution | rnmp wrote: | It's as if they remastered an old video game. So much more | detail! | avelis wrote: | To touch the stars. To reach a galaxy. To dream of afar. And in | the deepest space, see our ancestry. | throwaway4837 wrote: | It's hard to look at the Webb images without thinking that | there must be life and technology out somewhere else in the | stars. | quickthrower2 wrote: | Reading the selfish gene is making me think the same thing. | dylan604 wrote: | Why does that only come from Webb images? You weren't getting | that same sensation looking at the Hubble images before? If | that's true, then welcome to the club! It took you a bit | longer, but we're happy you're here now. ;P | 8bitsrule wrote: | The new scope appears to be capable of wonderful images, and no | doubt many new discoveries. | | Too bad, then, about the crappy colorizing/outlining for the 'so | pretty' crowd. I await the site that simply shows (frequency- | shifted) images. Any colorizing should have a 'legend' describing | its purpose. | jauntbox wrote: | Very cool to see several galaxies that were entirely invisible to | Hubble due to high redshift show up brightly to JWST. | systemvoltage wrote: | > This makes the Hubble telescope even more impressive in my | eyes. Built 50 years ago with presumably 60 year old tech. | | > > Hubble telescope was funded and built in the 1970s by the | United States space agency NASA with contributions from the | European Space Agency. Its intended launch was 1983, but the | project was beset by technical delays, budget problems, and the | 1986 Challenger disaster. Hubble was finally launched in 1990. | | I commented on this other thread: | https://news.ycombinator.com/item?id=32074242 | jcims wrote: | Advantages of IR incredibly apparent in the last pic. | | Very nicely done! | acqbu wrote: | Hubble = iPhone 4S; Webb = Galaxy S22 Ultra | UberFly wrote: | Considering these are just the initial "test" images there is | going to be some amazing stuff to come over the years. Can't | wait. | somenewaccount1 wrote: | Thank you so much!!! I really wanted to see the difference side | by side and this was an even better presentation. Really cool! | hexomancer wrote: | Just to be clear I did not create this website, I just saw it | on reddit. All credits to the original author: | https://www.reddit.com/r/woahdude/comments/vxeeqo/i_made_a_t... | dynm wrote: | 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 valid way of trying to understand things?) | spenczar5 wrote: | I worked in astronomy software for a few years for a different | telescope, the LSST. I am not an expert, but I was in this | world enough to answer. | | The short version - it converges faster (probably like 5-10x | faster), but also (as everyone else said) works in different | wavelengths. | | You can think of a telescope as a "photon bucket." The number | of photons it collects is proportional to the area of the | aperture. Webb's aperture area is 25.4 square meters, while | Hubble's is 4 square meters, so roughly speaking JWST will get | photons about 6 times quicker than Hubble. | | But that's only the roughest measure. Once you've got the | photons, what do you do with them? You send them to a detector. | There's loss in this process - you bounce off of mirrors, with | some small loss. You pass through band filters to isolate | particular colors, which have more loss. The detector itself | has an efficiency; in CCD cameras people speak of "quantum | efficiency" - the probability that a photon induces a charge | that can be counted when you read out the chip. That quantum | efficiency depends on the photon's wavelength. | | Furthermore - the longer your exposure, the more cosmic rays | you get which corrupt pixels. You can flush the CCD more often | and detect the cosmic rays and eliminate them, but you'll | eventually brush against the CCD's read-out noise, which is a | "tax" of noise you get every time you read out data. | | So this all get's complicated! People spend many years | characterizing detection capabilities of these instruments, and | write many pages on them. | | JWST's capabilities are described here: https://jwst- | docs.stsci.edu/jwst-near-infrared-camera/nircam... | | HST's camera is more complicated to characterize, partly | because it's older. Radiation has damaged and degraded many of | the components so they have a lot of noise. The details of how | this works are at the edge of human knowledge, so we don't have | a great model for them. From the STIS handbook: | Radiation damage at the altitude of the HST orbit causes the | charge transfer efficiency (CTE) of the STIS CCD to degrade | with time. The effect of imperfect CTE is the loss of signal | when charge is transferred through the CCD chip during the | readout process. As the nominal read-out amplifier (Amp D) is | situated at the top right corner of the STIS CCD, the CTE | problem has two possible observational consequences: (1) making | objects at lower row numbers (more pixel-to-pixel charge | transfers) appear fainter than they would if they were at high | row numbers (since this loss is suffered along the parallel | clocking direction, it is referred to as parallel CTE loss); | and (2) making objects on the left side of the chip appear | fainter than on the right side (referred to as serial CTE | loss). In the case of the STIS CCD, the serial CTE loss has | been found to be negligible for practical purposes. Hence we | will only address parallel CTE loss for the STIS CCD in this | Handbook. The current lack of a comprehensive | theoretical understanding of CTE effects introduces an | uncertainty for STIS photometry. | | Now - this was all about how _many_ photons you collect. When | humans look at an image, they also care a lot about how fine | the details are on it. This has to do with the resolution of | the telescope 's imaging systems. Resolution is limited by the | number of pixels on the detector, and (to a much lesser extent) | by the optical train of the telescope - the aberrations and | distortions introduced by mirrors that focus light onto the | detector's pixels. | | Hubble has a high-res camera, and a separate wide-angle camera. | Hubble's high-res camera actually outperforms JWST - it can | resolve down to 0.04 arcsec, while JWST's can go to around 0.1 | arcsec. But JWST's camera has a much wider field of view. | mtlmtlmtlmtl wrote: | 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... | lttlrck wrote: | Plus, upgrading Hubble wouldn't get us close either. JWST is | specifically designed to shield the sensors from IR/heat, and | it's 1 million miles from Earth for a similar reason. | nomel wrote: | > That is ~6.25 times the light collection area of | Hubble(25.4m2 vs 4m2) | | This would have to be scaled by the wavelength being | observed, for a resolution comparison. Hubble actually has | better absolute resolution, when viewing shorter the | wavelengths that JWT can't sense (0.05 arcseconds vs JWT 0.1 | arcseconds). | mtlmtlmtlmtl wrote: | Right, that didn't occur to me at first, but is just | obviously true when you point it out, thanks. Though I | didn't know that hubble is actually higher resolution in | that comparison. | | Then, in some sense, the first part of my explanation is | most of the story in the case of comparing MIRI(mid- | infrared instrument) to hubble in the near-infrared. | | But in comparing NIRCAM to Hubble in the near-infraread | JWST would in fact have greater resolution, no? | dylan604 wrote: | 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. | 0xfaded wrote: | 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 | red_trumpet wrote: | 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. | dredmorbius wrote: | There's effectively _no_ motion blur visible. | | The most pronounced effects _might_ be paralax of _nearby_ | stars to thousands of light-years at the outside. That would | be observable in images taken _at opposite sides of Earth 's | orbit around the Sun_, a baseline of about 300 million km | (186 million miles). Even _that_ will be phenomenally small, | too small to be observable _for most objects within our own | galaxy_ (the Milky Way) let alone the distant objects JWST is | most concerned with. | | From Wikipedia: | | _In 1989 the satellite Hipparcos was launched primarily for | obtaining parallaxes and proper motions of nearby stars, | increasing the number of stellar parallaxes measured to | milliarcsecond accuracy a thousandfold. Even so, Hipparcos is | only able to measure parallax angles for stars up to about | 1,600 light-years away, a little more than one percent of the | diameter of the Milky Way Galaxy._ | | _The Hubble telescope WFC3 now has a precision of 20 to 40 | microarcseconds, enabling reliable distance measurements up | to 3,066 parsecs (10,000 ly) for a small number of stars.[10] | This gives more accuracy to the cosmic distance ladder and | improves the knowledge of distances in the Universe, based on | the dimensions of the Earth 's orbit._ | | https://en.wikipedia.org/wiki/Stellar_parallax | | JWST's optical acuity is roughly similar to Hubble --- | despite the larger mirror surface, it's using longer | wavelengths of electromagnetic radiation, with lower | resolving power. | | Movement of the JWST itself is kept to an absolute minimum | for obvious reasons. It would simply be unusable as a | telescope if this weren't the case. | | Absolute motion of objects being imaged ... also isn't a | factor, as the maximum resoultion of JWST (the smallest | pixels on an image) are still tremendous. It's _possible_ | that a nearbye (neighbouring galaxy) nova event _might_ | generate observable motion _over days or weeks_ , but even | that is unlikely. The interesting stuff in that event is | actually the changes in brightness and evolution of light | emissions, for the most part. | | In the case of the Carina Nebula image 8,500 light years | distant (that is, astronomically _near_ ), the individual | dust segments are _light years_ in length. The distance from | the Earth to the Sun is roughly 1 /64,000th that distance --- | too small to visualise in thos images. The individual stars | show are not dots or disks, but points, whose apparent size | is a matter of refraction and saturation effects on the JWST | itself. | | Even where there _migh_ be any movement, individual images | are composed of multiple exposures and "stacked" to take | median observed signal strengths. This is, in a way, to | eliminate motion effects, but the moving entities are cosmic | rays which create random signatures on the sensors of JWST, | and not movement of the telescope or its targets themselves. | IshKebab wrote: | Motion of what? | dontlistentome wrote: | everything everywhere all at once | spookthesunset wrote: | Minor changes to the satellite position? Vibration from | some hardware? I dunno but the parent asks a question I ask | too. | | When you do long exposure, any kind of movement, even very | small, can degrade your image. | | How JWST handles movement during long exposure is a good | question. Same with hubble. | adgjlsfhk1 wrote: | long exposure images aren't actually 1 continuous | exposure. you take a ton of individual images and | composite them using known reference points. | ryneandal wrote: | Well I mean the JWST is in orbit both around the L2 point | and the sun. It's sensitive equipment must also be facing | away from the sun. So there's a lot of movement going on | out there. | dylan604 wrote: | I'm sorry but no no no. These telescopes are tracking the | objects they are imaging specifically to avoid imaging issues | from motion. This isn't some dude in the backyard with an | alt-az scope bought from a Sears catalog. | | I really hope you were trolling with this response | ryneandal wrote: | Here's out exposure time works for JWST: https://jwst- | docs.stsci.edu/understanding-exposure-times | pythonguython wrote: | 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. | mtlmtlmtlmtl wrote: | This is true, but he was asking specifically about a metric | that's independent of the exposure time. | unethical_ban wrote: | 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. | rdsubhas wrote: | A crude analogy is like this: Two cameras are pointed towards a | wall. Camera #1 is good, but it is blocked by the wall. Camera | #2 has a special trick, it does some magic that can look behind | the wall. | | Now both have resolutions and stuff. But no matter how big the | resolution or how long it stares, cam1 is fundamentally blocked | by the wall. It can take extremely high res photos of things | inside the wall, but it can never see anything behind the wall. | | Cam2 could have infinitely higher quality than cam1 -- because | who knows, there can be 100, 1000, million or a never ending | world of things behind that wall that can never be seen or | captured by cam1. | | Cam1 is Hubble, cam2 is jwst, and the wall is infrared | wavelength which is all around us. JWST can peer deeper and | find hidden things into the _same point_ in space, which Hubble | cannot because of it 's infrared wall. | Osmium wrote: | 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. | agrajag wrote: | 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. | masterspy7 wrote: | Not trying to underscore this incredible achievement, but I'm | curious if we could use AI techniques to upscale the Hubble | images to achieve similar results as the Webb telescope. Has this | been tried before? | wetpaws wrote: | No | lynguist wrote: | It's a valid thought, but it would really be like trying to | take pictures of the sky from underwater and using AI to make | it look like it was taken from out of water. | | This means: the AI has to predict what it is supposed to look | like and for that we would need out of water pictures as | reference in the first place which we didn't so far! | | And then: even if we have these new out of water pictures as | reference, the AI generated ones would still not show what is | real, but instead a fiction. The fiction can look believable | but it cannot be studied to derive facts from it. It's like | trying to study an AI generated language. | | This sounds like my friend who literally believes that buses | will go extinct within 3-5 years as every vehicle will self | drive. It's not thought all the way through. | detaro wrote: | AI upscaling works if you want a prettier picture, but not if | you want to actually _know_ more. AI can 't magically conjure | information that isn't there, so if you upscale it has to | invent details to fill in. Which is fine for some use cases, | but not for science or truth-finding. | Kelm wrote: | Sure you could try, but without getting real higher fidelity | photos you'd never know how realistic the synthetic images are. | [deleted] | alberth wrote: | Why is there so much more lens flare on Webb vs Hubble? | | It seems to negatively degrade the photos taken much more so than | Hubble. | Dave_Rosenthal wrote: | The segmented design of the mirror creates diffraction effects | vs. Hubble's single mirror. | kristofferR wrote: | This is a great explanation: https://bigthink.com/starts-with- | a-bang/james-webb-spikes/ | libraryatnight wrote: | This is interesting, thank you - going to pass this along to | friends who were curious and got less informative answers :) ___________________________________________________________________ (page generated 2022-07-12 23:00 UTC)