Registrations are currently delayed due to a spam wave, please bear with me.

James Webb Space Telescope

Started by Alberon, December 24, 2021, 12:17:20 AM

Previous topic - Next topic

Replies From View

Quote from: Cuellar on January 06, 2022, 01:12:48 PMSorry been trying to find a good pic, here's one from a couple of christmases ago

Weird theme for Christmas.  Massive paper hat and joke inside maybe


Think this big foil wally has got its wings out now. Most of the things that could have gone wrong out the way now.


Don't say that!

It'll get into position and they'll realise they've left the lens cap on or something.


Or someone'll have dropped an Extra Strong Mint or a Fisherman's Friend or summat, and the heat from that'll destroy the images.


Quote from: Alberon on January 08, 2022, 06:55:44 PMDon't say that!

It'll get into position and they'll realise they've left the lens cap on or something.


With the telescope now in the unpacked position work can begin to align the hexagonal segments that make up the primary mirror.

Quote from: NASAThe primary mirror segments and secondary mirror are moved by six actuators that are attached to the back of each mirror piece. The primary mirror segments also have an additional actuator at its center that adjusts its curvature.

QuoteEach of the 18 segments of the primary mirror is plated in a shiny, but ultra thin, layer of gold. If left in launch position, they would act as individual telescopes with images that would be fuzzy and unclear. Once aligned, the mirror segments will act as one giant mirror 21.3 feet (6.5 meters) across, the largest ever in space.

NASA has estimated that it could take up to 120 days after launch for Webb's mirror alignment work to be complete. The first photos from Webb are not expected until about five months after launch once commissioning ends.


"And the I move this mirror... just a tiny amount..."

All Surrogate

I don't want to jinx it, but I'm very happy that things are going so well. Yay Science!

Replies From View


When will we be seeing the first pictures of alien tits?


Quote from: Fr.Bigley on January 10, 2022, 01:01:42 AMWhen will we be seeing the first pictures of alien tits?

Ask your mum.


She said sometime in July, according to her department in astro physics and steak pie theory.

Uncle TechTip

An interesting page comparing Hubble and JWST. The new telescope has a mirror almost 3 times as big as Hubble. It also sets expectations of what we will actually see - these won't be beautiful full colour images, I hope everyday people aren't disappointed.

I also read that when you go out and look at the average bright star, about a million photons emitted by that star are hitting your retina, every second. JWST will be looking at sources as low as one photon per second.


As far as I am aware all of the beautiful Hubble images we know and love are false/enhanced colour anyway - eg don't reflect what they'd look like if your eyes were acute enough to see them (or they were a lot nearer). So there is no reason why jwst images shouldn't be processed to be just as impressive.


I think it's less that they are enhanced and more that they are depicting light frequencies not visible to us, so they do not represent what that area would look like to the naked eye. I suppose they are probably guilty of using beautiful colours in lieu of the invisible ones. They could have made the universe look literally shitty.


Astronomical images are often made by photographing one type of light and giving it one colour, then photographing a different type of light and giving it a separate colour, and so on. Taking something like Hubble's Pillars of Creation, Wiki says that:

QuoteThe photograph was made with light emitted by different elements in the cloud and appears as a different color in the composite image: green for hydrogen, red for singly ionized sulfur and blue for double-ionized oxygen atoms.

I'm sure the composited images are then also enhanced and colour corrected so that the various elements can be distinguished from each other and so that they look really good - those headline images are more PR than science, and help to justify the costs of missions to the general public who might otherwise bang on about whether it helps starving kids. Except it absolutely won't stop those people from banging on, of course.


I found another couple of pictures (not taken by Hubble) that show the difference between false colour and real colour.

The picture on the right is the real colour one taken using red, green and blue filters. The one of the left is the false colour one that uses just specific wavelengths. There's so much hydrogen that the true colour photo is just drowned out in red.

QuoteWe have an "SHO" image, or an image that blocks out all signal except for very precise lines of emission. In this case, SII, Hα, and OIII. These wavelengths are typically assigned colors in post processing, where SII = Red, Hα = Green, and OIII = Blue. In actuality, this is where they actually are in the "visible" color spectrum. Since Hydrogen is by far the dominant gas in most emission nebulae (see the image on the right being nothing but red), we get mostly nothing but green in an SHO image to begin with. After subtracting the green though, we are left only with how the Hα interacts with the SII and the OIII giving us a nice contrasting gold and blue color that shows the complexity of the nebula's composition.


Thanks to public funding for NASA and the ESA and other organisations who send observatories to space, there's tons of raw data from the telescopes which is freely available online. There's software out there which allows for making your own choice of spectra from a given image which you can then turn into your own lurid false colour images. I can't remember which specific software I had a play around with, but I followed some guide online probably about ten years ago and quickly realised that it's way, way, way more complicated than adjusting colours on a digital camera image.

Dex Sawash


Probably the space anus that just dropped those.


It's a common misconception that the image has been censored, but the reality is that one of these things moved through the view when they pressed the shutter


Quote from: Dex Sawash on January 11, 2022, 12:22:18 PMWhat sort of space filth have the censored at the top right?
look if they pointed the telescope at those squares another 10 million children would have starved to death. Is that what you want


Mirror deployment is now complete and just one more stage remains - the final course correction burn to put the telescope in orbit of the L2 point. That should be happening some time on Monday.


It's arrived at L2
QuoteToday, at 2 p.m. EST, Webb fired its onboard thrusters for nearly five minutes (297 seconds) to complete the final postlaunch course correction to Webb's trajectory. This mid-course correction burn inserted Webb toward its final orbit around the second Sun-Earth Lagrange point, or L2, nearly 1 million miles away from the Earth.

The final mid-course burn added only about 3.6 miles per hour (1.6 meters per second) – a mere walking pace – to Webb's speed, which was all that was needed to send it to its preferred "halo" orbit around the L2 point.

Bored now!


Only four months until we start getting photos!

Replies From View

Replies From View

Quote from: NoSleep on January 11, 2022, 12:29:29 PMProbably the space anus that just dropped those.

Sorry; hadn't yet read NoSleep's own answer.


I still can't get my head around how its orbit works.

Replies From View

Quote from: Milo on January 24, 2022, 08:57:54 PMI still can't get my head around how its orbit works.

It simply gets chewed and creates a very minty breath indeed.